Unexpected slowdowns at overhang corners

[loudaslife]

Description of the bug

I'm printing an item with a large 45° overhang surface, and for functional purposes this surface needs to be reasonably flat. However, the printer slows down and creates over-extruded ridges near the edges.

The natural assumption would be that this is the result of the firmware deceleration to navigate a sharp corner, but I deliberately rounded these edges to prevent that. The gcode preview makes it clear that the slicer is deliberately slowing down.

The overhang doesn't become any steeper around this corner, so in theory, dynamic overhang speed shouldn't be slowing it down. But given that it slows down to exactly 15mm/s, I think the dynamic overhang code is misinterpreting these segments as having <25% overlap, even though they appear to have >50%.

It's also unusual that the slowdown becomes progressively more severe towards the top of the part, even though the geometry of the corner is identical at every layer.

Project file & How to reproduce

Corner Plane 3.zip

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

2.8.1+win64

Operating system

Windows 11

Printer model

Prusa MK4S