priming line isn't set

[kb9ysc]

Description of the bug

When I tried to use paint-on supports, the priming line at the start was left as the default extruder. (extruder 1 on the MMU2s?)

I uploaded it to octoprint and when I sent it to my printer, the plugin that I use to select the filament for single-material prints popped up asking me to select the filament. I picked filament 3. it then started the printing process, but then immediately after doing the priming line, it switched from filament 3 to filament 2. when it did so, it continued printing, but since it had just switched, the printer did not have plastic all the way to the tip, so it printed nothing. I stopped the print, reset everything, and then started it again. the same behavior occured, but this time I selected filament 2. it then printed normally.

What I'd expect is that it should just pick the correct filament at the start and just print without needed the filament selected.

I've attached the project file as well as the gcode that was generated.

Project file & How to reproduce

Archive.zip

Checklist of files included above

• [X] Project file
• [x] Screenshot

Version of PrusaSlicer

Version 2.6.0-alpha6+MacOS-x64

Operating system

OS X Ventura 13.2.1

Printer model

Mk3s

[kb9ysc]

I added a screenshot showing that the prime line is in blue (filament 1).