Small areas infill overlapping with infill every n layer

[mieszkokl]

Describe the bug Using infill every n layer option small areas where larger infill doesn't fit, smaller one is used. The problem is that on some layers these infill overlaps. You can see examples on attached screenshots. I would be grateful for info if it's only a configuration issue or maybe a bug in the code and if it's a bug any hint about how to fix it would be very helpful.

To Reproduce Steps to reproduce the behavior:

1. Open the stl file from attached archive
2. Load the print ini configuration from attached archive
3. See the gcode output for the model - it will be like shown on screenshots above

3D Model and Slic3r Configuration Export issue_config_and_model.zip

Expected behavior I expect the infill generated with thinner extrusion doesn't overlap with the thicker one.

Screenshots

Desktop (please complete the following information):

• OS: Windows 11
• Version 1.3.0

[mieszkokl]

I would be grateful for a hint where I can find the logic responsible for that in the code, so I can fix it myself.

[supermerill]

smell like a thin_wall / gapfill bug.

[mieszkokl]

I found out that's the code in LayerRegionFill.cpp lines from 126-151 (master branch) that is responsible for making this extra filling. The issue is only on layers where normally there is no infill because of the "infill every n layer" setting. On layers where we have both normal infill and this extra one they're correctly placed. Do you have any idea what went wrong?