MMU2 won't change filament during a print
So, after much tweaking, replacing of tubes, printing of new selector, new cutting block, I have it set now that I can manually "load to nozzle" any of the five filaments and they all work just fine. The initial loading doesn't work so well, but if I do it by hand and then tighten the idler, it seems to work. Manually.
Prints, though, it doesn't. I've tried setting up a 5-color test in PrusaSlicer and just to rule out me being an idiot, I downloaded the gcode for a 5-color test from Prusaprinters.org. Everything I try has the same outcome:
First, it will warm up and do the bed leveling. Then it will return to home and unload whatever filament is in the nozzle, switch to the first color, load it up, and purge the nozzle. Then it will proceed with printing the wipe tower, the skirt, and then the print itself. At this point, everything is working just fine.
When it comes time for a color change, though, it moves to the wipe tower, slows way down, then does something with the extruder. I'm not sure what, but it looks like it pulls the filament out for half a second (I can see the door "close" with the lack of filament in the gears) and then immediately (and I mean immediately) shoves the same filament back in and starts to wipe. It will do this with every supposed-to-be-a-color-change.
Finda seems to be fine when I manually test it, and the MMU works fine for loading and unloading when I do it manually.
I'm out of ideas and super-frustrated with this thing.