I'm still trying to dial in my MMU as well, but I couldn't believe that nobody had responded to your post yet so I'll throw in my two cents. I've been calibrating my filament closer to the bottom of the extruder gear, right at where the PTFE tube starts per some comments from another user who is seeing some success. I've had a hard time getting Hatchbox to work well with my printer and I've read a couple other posts where they have had a hard time with it as well, which sucks because I have a lot of Hatchbox filament and I normally really like it. It seems like it always creates stringy tips in my experience and grinds more easily. I do try to print at the lowest possible temperature allowed by the filament I'm using, which seems to help.