diff --git a/src/Evolution/Executables/RadiationTransport/MonteCarlo/EvolveMonteCarlo.hpp b/src/Evolution/Executables/RadiationTransport/MonteCarlo/EvolveMonteCarlo.hpp
index 8f90a3c796749..e1bdde9784fd1 100644
--- a/src/Evolution/Executables/RadiationTransport/MonteCarlo/EvolveMonteCarlo.hpp
+++ b/src/Evolution/Executables/RadiationTransport/MonteCarlo/EvolveMonteCarlo.hpp
@@ -201,11 +201,11 @@ struct EvolutionMetavars {
               Parallel::Phase::Evolve,
               tmpl::list<
                   Actions::AdvanceTime,
-                  evolution::Actions::RunEventsAndTriggers,
+                  evolution::Actions::RunEventsAndTriggers<false>,
                   Actions::AdvanceTime,
-                  evolution::Actions::RunEventsAndTriggers,
+                  evolution::Actions::RunEventsAndTriggers<false>,
                   Actions::AdvanceTime,
-                  evolution::Actions::RunEventsAndTriggers,
+                  evolution::Actions::RunEventsAndTriggers<false>,
                   Particles::MonteCarlo::Actions::SendDataForMcCommunication<
                       volume_dim,
                       // No local time stepping
diff --git a/src/Evolution/Particles/MonteCarlo/Actions/InitializeMonteCarlo.hpp b/src/Evolution/Particles/MonteCarlo/Actions/InitializeMonteCarlo.hpp
index f5ecaf298f3be..8838277839dc5 100644
--- a/src/Evolution/Particles/MonteCarlo/Actions/InitializeMonteCarlo.hpp
+++ b/src/Evolution/Particles/MonteCarlo/Actions/InitializeMonteCarlo.hpp
@@ -49,8 +49,8 @@ namespace Initialization::Actions {
 /// - Adds:
 ///   * Particles::MonteCarlo::Tags::PacketsOnElement
 ///   * Particles::MonteCarlo::Tags::RandomNumberGenerator
-///   * Particles::MonteCarlo::Tags::DesiredPacketEnergyAtEmission
-///       <NeutrinoSpecies>
+///   * Particles::MonteCarlo::Tags::DesiredPacketEnergyAtEmission<
+///                                  NeutrinoSpecies>
 ///   * Particles::MonteCarlo::Tags::CellLightCrossingTime<DataVector>
 ///   * Background hydro variables
 ///   * Particles::MonteCarlo::Tags::MortarDataTag<dim>
@@ -117,7 +117,7 @@ struct InitializeMCTags {
         tmpl::list<Particles::MonteCarlo::Tags::PacketsOnElement>>(
         make_not_null(&box), std::move(all_packets));
 
-    unsigned long seed =
+    const unsigned long seed =
         std::random_device{}();  // static_cast<unsigned long>(time(NULL));
     typename Particles::MonteCarlo::Tags::RandomNumberGenerator::type rng(seed);
 
diff --git a/src/Evolution/Particles/MonteCarlo/GhostZoneCommunication.hpp b/src/Evolution/Particles/MonteCarlo/GhostZoneCommunication.hpp
index d11ba5cedcc30..0ced96571ea55 100644
--- a/src/Evolution/Particles/MonteCarlo/GhostZoneCommunication.hpp
+++ b/src/Evolution/Particles/MonteCarlo/GhostZoneCommunication.hpp
@@ -136,6 +136,16 @@ struct GhostDataMcPackets {
         const size_t d = max_distance_direction.value().dimension();
         const Side side = max_distance_direction.value().side();
         packet.coordinates.get(d) += (side == Side::Lower) ? (2.0) : (-2.0);
+        // Corner/edge treatment; move packet in a live point for now
+        // Definitely needs improvement...
+        for (size_t dd = 0; dd < Dim; dd++) {
+          if (dd != d && packet.coordinates.get(dd) < -1.0) {
+            packet.coordinates.get(dd) = -2.0 - packet.coordinates.get(dd);
+          }
+          if (dd != d && packet.coordinates.get(dd) > 1.0) {
+            packet.coordinates.get(dd) = 2.0 - packet.coordinates.get(dd);
+          }
+        }
         if (output.contains(max_distance_direction.value())) {
           output[max_distance_direction.value()].push_back(packet);
         }
diff --git a/src/ParallelAlgorithms/Events/ObserveTimeStep.hpp b/src/ParallelAlgorithms/Events/ObserveTimeStep.hpp
index 63751cb189d01..b736c560ceb41 100644
--- a/src/ParallelAlgorithms/Events/ObserveTimeStep.hpp
+++ b/src/ParallelAlgorithms/Events/ObserveTimeStep.hpp
@@ -165,18 +165,21 @@ class ObserveTimeStep : public Event {
   // We obtain the grid size from the variables, rather than the mesh,
   // so that this observer is not DG-specific.
   using argument_tags =
-      tmpl::list<::Tags::TimeStep>;  //, typename System::variables_tag>;
+      tmpl::list<::Tags::TimeStep, typename System::variables_tag>;
 
   template <typename ArrayIndex, typename ParallelComponent,
             typename Metavariables>
   void operator()(const TimeDelta& time_step,
-                  // const typename System::variables_tag::type& variables,
+                  const typename System::variables_tag::type& variables,
                   Parallel::GlobalCache<Metavariables>& cache,
                   const ArrayIndex& array_index,
                   const ParallelComponent* const /*meta*/,
                   const ObservationValue& observation_value) const {
-    const size_t number_of_grid_points =
-        1;  // variables.number_of_grid_points();
+    size_t number_of_grid_points = 1;
+    if constexpr (not std::is_same_v<typename System::variables_tag::tags_list,
+                                       tmpl::list<>>) {
+      number_of_grid_points = variables.number_of_grid_points();
+    }
     const double slab_size = time_step.slab().duration().value();
     const double step_size = abs(time_step.value());
     const double wall_time = sys::wall_time();
diff --git a/tests/Unit/Evolution/Particles/MonteCarlo/Test_CellVolume.cpp b/tests/Unit/Evolution/Particles/MonteCarlo/Test_CellVolume.cpp
index 4c8cc0adfb8bb..61ac032d2d0be 100644
--- a/tests/Unit/Evolution/Particles/MonteCarlo/Test_CellVolume.cpp
+++ b/tests/Unit/Evolution/Particles/MonteCarlo/Test_CellVolume.cpp
@@ -15,10 +15,12 @@ SPECTRE_TEST_CASE("Unit.Evolution.Particles.MonteCarloCellVolume",
                      Spectral::Quadrature::CellCentered);
 
   const size_t dv_size = 27;
-  DataVector zero_dv(dv_size, 0.0);
-  Scalar<DataVector> lapse{DataVector(dv_size, 1.2)};
-  Scalar<DataVector> sqrt_determinant_spatial_metric{DataVector(dv_size, 0.9)};
-  Scalar<DataVector> det_jacobian_logical_to_inertial{DataVector(dv_size, 1.1)};
+  const DataVector zero_dv(dv_size, 0.0);
+  const Scalar<DataVector> lapse{DataVector(dv_size, 1.2)};
+  const Scalar<DataVector> sqrt_determinant_spatial_metric
+    {DataVector(dv_size, 0.9)};
+  const Scalar<DataVector> det_jacobian_logical_to_inertial
+    {DataVector(dv_size, 1.1)};
   const double time_step = 0.6;
 
   Scalar<DataVector> cell_proper_four_volume{DataVector(dv_size, 0.0)};
diff --git a/tests/Unit/Evolution/Particles/MonteCarlo/Test_CommunicationTags.cpp b/tests/Unit/Evolution/Particles/MonteCarlo/Test_CommunicationTags.cpp
index a91b6f4c8f5e4..46aaa87fdf8a3 100644
--- a/tests/Unit/Evolution/Particles/MonteCarlo/Test_CommunicationTags.cpp
+++ b/tests/Unit/Evolution/Particles/MonteCarlo/Test_CommunicationTags.cpp
@@ -524,6 +524,10 @@ void test_send_receive_actions() {
   // topological coordinate of their new element.
   packet_east.coordinates[0] -= 2.0;
   packet_south.coordinates[1] += 2.0;
+  // Current hack for edges/corners
+  if constexpr (Dim > 2){
+    packet_south.coordinates[2] = -2.0 - packet_south.coordinates[2];
+  }
   {
     const auto& east_data = ActionTesting::get_inbox_tag<
         comp, Particles::MonteCarlo::McGhostZoneDataInboxTag<
diff --git a/tests/Unit/Evolution/Particles/MonteCarlo/Test_TakeTimeStep.cpp b/tests/Unit/Evolution/Particles/MonteCarlo/Test_TakeTimeStep.cpp
index 1314fb15ccdfd..15ebadbc052fe 100644
--- a/tests/Unit/Evolution/Particles/MonteCarlo/Test_TakeTimeStep.cpp
+++ b/tests/Unit/Evolution/Particles/MonteCarlo/Test_TakeTimeStep.cpp
@@ -33,15 +33,15 @@ void test_flat_space_time_step() {
   const size_t num_ghost_zones = 1;
 
   const size_t dv_size = cube(size_1d);
-  DataVector zero_dv(dv_size, 0.0);
+  const DataVector zero_dv(dv_size, 0.0);
   const size_t dv_size_with_ghost = cube(size_1d + 2 * num_ghost_zones);
-  DataVector zero_dv_with_ghost(dv_size_with_ghost, 0.0);
+  const DataVector zero_dv_with_ghost(dv_size_with_ghost, 0.0);
   const size_t dv_size_in_ghost = square(size_1d) * num_ghost_zones;
-  DataVector zero_dv_in_ghost(dv_size_in_ghost, 0.0);
-  DataVector one_dv_in_ghost(dv_size_in_ghost, 1.0);
+  const DataVector zero_dv_in_ghost(dv_size_in_ghost, 0.0);
+  const DataVector one_dv_in_ghost(dv_size_in_ghost, 1.0);
 
   // Minkowski metric
-  Scalar<DataVector> lapse{DataVector(dv_size, 1.0)};
+  const Scalar<DataVector> lapse{DataVector(dv_size, 1.0)};
   tnsr::II<DataVector, 3, Frame::Inertial> inv_spatial_metric =
       make_with_value<tnsr::II<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
   inv_spatial_metric.get(0, 0) = 1.0;
@@ -52,14 +52,14 @@ void test_flat_space_time_step() {
   spatial_metric.get(0, 0) = 1.0;
   spatial_metric.get(1, 1) = 1.0;
   spatial_metric.get(2, 2) = 1.0;
-  Scalar<DataVector> sqrt_determinant_spatial_metric(dv_size, 1.0);
-  tnsr::I<DataVector, 3, Frame::Inertial> shift =
+  const Scalar<DataVector> sqrt_determinant_spatial_metric(dv_size, 1.0);
+  const tnsr::I<DataVector, 3, Frame::Inertial> shift =
       make_with_value<tnsr::I<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
-  tnsr::i<DataVector, 3, Frame::Inertial> d_lapse =
+  const tnsr::i<DataVector, 3, Frame::Inertial> d_lapse =
       make_with_value<tnsr::i<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
-  tnsr::iJ<DataVector, 3, Frame::Inertial> d_shift =
+  const tnsr::iJ<DataVector, 3, Frame::Inertial> d_shift =
       make_with_value<tnsr::iJ<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
-  tnsr::iJJ<DataVector, 3, Frame::Inertial> d_inv_spatial_metric =
+  const tnsr::iJJ<DataVector, 3, Frame::Inertial> d_inv_spatial_metric =
       make_with_value<tnsr::iJJ<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
 
   // Mesh velocity set to std::null for now
@@ -90,7 +90,7 @@ void test_flat_space_time_step() {
   inverse_jacobian_logical_to_inertial.get(0, 0) = 1.0;
   inverse_jacobian_logical_to_inertial.get(1, 1) = 1.0;
   inverse_jacobian_logical_to_inertial.get(2, 2) = 1.0;
-  Scalar<DataVector> det_jacobian_logical_to_inertial(dv_size, 1.0);
+  const Scalar<DataVector> det_jacobian_logical_to_inertial(dv_size, 1.0);
 
   // Coordinates
   tnsr::I<DataVector, 3, Frame::ElementLogical> mesh_coordinates =
diff --git a/tests/Unit/Evolution/Particles/MonteCarlo/Test_TimeStepAction.cpp b/tests/Unit/Evolution/Particles/MonteCarlo/Test_TimeStepAction.cpp
index f3352014704d2..d7dca4d480ee8 100644
--- a/tests/Unit/Evolution/Particles/MonteCarlo/Test_TimeStepAction.cpp
+++ b/tests/Unit/Evolution/Particles/MonteCarlo/Test_TimeStepAction.cpp
@@ -88,11 +88,11 @@ struct component {
                   Frame::Inertial>,
       Tags::deriv<gr::Tags::Shift<DataVector, Dim>, tmpl::size_t<Dim>,
                   Frame::Inertial>,
-      Tags::deriv<gr::Tags::InverseSpatialMetric<DataVector, Dim>,
+      Tags::deriv<gr::Tags::SpatialMetric<DataVector, Dim>,
                   tmpl::size_t<Dim>, Frame::Inertial>,
       gr::Tags::SpatialMetric<DataVector, Dim, Frame::Inertial>,
       gr::Tags::InverseSpatialMetric<DataVector, Dim, Frame::Inertial>,
-      gr::Tags::DetSpatialMetric<DataVector>,
+      gr::Tags::SqrtDetSpatialMetric<DataVector>,
       evolution::dg::subcell::Tags::Coordinates<Dim, Frame::ElementLogical>,
       domain::Tags::MeshVelocity<Dim>,
       evolution::dg::subcell::fd::Tags::InverseJacobianLogicalToInertial<Dim>,
@@ -192,8 +192,8 @@ void test_advance_packets() {
       make_with_value<tnsr::i<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
   tnsr::iJ<DataVector, 3, Frame::Inertial> d_shift =
       make_with_value<tnsr::iJ<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
-  tnsr::iJJ<DataVector, 3, Frame::Inertial> d_inv_spatial_metric =
-      make_with_value<tnsr::iJJ<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
+  tnsr::ijj<DataVector, 3, Frame::Inertial> d_spatial_metric =
+      make_with_value<tnsr::ijj<DataVector, 3, Frame::Inertial>>(lapse, 0.0);
 
   // Fluid variables
   Scalar<DataVector> rest_mass_density(zero_dv);
@@ -313,7 +313,7 @@ void test_advance_packets() {
        shift,
        d_lapse,
        d_shift,
-       d_inv_spatial_metric,
+       d_spatial_metric,
        spatial_metric,
        inv_spatial_metric,
        sqrt_determinant_spatial_metric,