Drag & Drop from outside an iframe into an iFrame not working

[broncha]

Hi!

I have this code,

<DragDropContextProvider backend={MultiIframeBackend}>
        <div>
          <EditorToolbar 
            toggleComponents={this.handleToggle}
            componentPanelOpen={this.state.drawerOpen}
            value={this.state.value} 
            onChange={this.handleChange} 
            onDeviceChange={this.handleDeviceChange}
          />
          <ComponentDrawer drawerOpen={drawerOpen} />
          <Frame 
            mountTarget={mountTarget}
            initialContent={initialContent}
            style={{
              border:'none', 
              outline: 'medium none',
              width: sizes[device].width, 
              height: sizes[device].height, 
              transition: 'width 0.35s ease',
              margin: '0 auto',
              display: 'block'
            }}
            >
              <Canvas />
            </Frame>
        </div>
        </DragDropContextProvider>

I am dragging items from ComponentDrawer to Canvas in the Frame.
Canvas is the DropTarget
I can see that the state of DropTarget(Canvas) changing to canDrop: true, but I cant really drop anything in there.