Getting "File Incomplete" errors when using PrusaSlicer with a particular configuration  

Getting "File Incomplete" errors when using PrusaSlicer with a particular configuration

I'm about a week into my Prusa journey, and starting to dig into some calibration processes to learn the ropes. I am trying to follow the steps here to address stringing issues: https://projects.ttlexceeded.com/3dprinting_techniques_calibrating_retraction.html

It took me the better part of a day, but I was able to figure out how to set up the virtual multi-extruder profile. However everything that I slice using this profile now generates the "File Incomplete" error when starting the print from the SD card. Have checked the following things:

• Confirmed that I can slice and print other files from the default profile without this issue.
• Confirmed that the sliced file contains "; prusaslicer_config = end" as the last line.
• Manually added "MK3S" to the gcode printer model check.
• Painstakingly checked every single config field in the profile comparison tool to make sure the new Printer Profile I created had the same settings as the defaults (the profile management experience is horrid for a first timer!).

I can just click through and print anyway, but it would be nice to know what's causing this issue and if there are perhaps other problems here that I haven't discovered yet. It's not obvious how to attach gcode or config files here, but I can add a Dropbox link if that would help.

Thanks in advance!