Prusa XL Multi-Extruder Slicing changes color of first STL in one spot when it shouldn't

[BrienKing]

Description of the bug

I have 2 STL's that I imported into Prusa Slicer 2.6.1 and it asked if I wanted to join them, so I did.

Looking at it on the screen it looks correct as seen here:

When I slice it, it colors part of the red part in Yellow.

Project file & How to reproduce

I was able to cut the part down to the minimum to show off the issue.
Test Prusa XL Joust.zip

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

2.6.1

Operating system

Windows 10

Printer model

Prusa XL Dual Extruder (4.7.2)

[kubispe1]

Quite a tough issue.

• I would guess that this issue is related to wrong region detection. Where bridges somehow overflow to the middle part, where the top solid should be. Maybe some numeric issue.
• it is sensitive to print settings (only 0.40mm DRAFT does not work)
• PrusaSlicer-2.6.0-beta1 - Doesnot work
• PrusaSlicer-2.6.0-alpha6 - still work
• Also I would guess that it is a less frequest issue

[kubispe1]

there is a picture of wrong region detection:

[BrienKing]

I'll try a print at a lower layer height and see what happens for me.

[BrienKing]

Seems to be an issue with the .4 Layer Height, works at lower layer heights.

[BrienKing]

Posted to wrong issue, sorry.