yeah, haven't tried soluble filament yet, it was more for multi color, or an autoloader (it supports a feature called spool join, that would just move to the next spool when it runs out on the first one.) figured it would be useful if i ended up printing more ppe.
Yeah the filament sensor on the extruder needs to be calibrated perfectly otherwise it might think the filament might not have loaded correctly and keep trying. If it fails to load too many times then it pauses the print until it's resolved by a human
Also too much friction in the filament path could also cause issues. Took me 2 days to get it calibrated.
I also read somewhere that MMU support was added to marlin so not sure if it could be made to work on non-prusa printers using a MMU2S clone.