The cover part have issues. The center hole should be a cilinder that pushes the bearing to the correct place. i ve printed your cover and after a few hours i find out that the bearing moves to the outside (like 3mm) generating a missalignment with the gear. Due to this fact, the extruder doesnt extrudes correctly and eats the filament.
The part should be like this: https://www.thingiverse.com/thing:2044625
Note: i am using 3mm filament with all the titan extruder original parts except for the cover