I've been facing this problem since I started using the machine. I believe the opening in the filament feeder nuts is too small and often causes the filament to get stuck. As far as I can tell there are 3 nuts attached to the tubes and the filament (Maxx from leapfrog) often gets stuck until I find the exact angle and really jam it through them. Once they're in, it's mostly fine. Very annoying when loading new filament.
Recently some filament got stuck in the nut closest to the extruder and now I can't get it in or out. I tried to grab it with some pliers but the top just broke off. It's stuck and I can't easily remove the nut because a small standard adjustable wrench won't fit in the space to get hold of the nut.