Straightening filament.....
When loading filament into the MMU3, Prusa recommends straightening the filament from its natural curl as much as possible, which is understandable. However, I find it rarely straightens very much - do you use any tool or anything in particular to help straighten the few inches or so at the end prior to loading?
RE:
I think, at first, I was much more careful about trying to straighten the filament and make sure it was cut at a proper angle for loading into the MMU -- I feed from a dry box, into an enclosure, and it has to pass through a few fitting connectors along the way, and that's where I find it often catches. But over time, I've been much less attentive -- I find if I can pass it through the fitting connectors, everything works, and I can apply a small amount of force if the MMU doesn't catch it.
As to straightening, I just pull the filament between pinched fingers a few times, and that seems to be enough.
RE: Straightening filament.....
https://www.printables.com/model/4385-lmgts-filament-straightener
this seems to work pretty good.