I haven't had any real issues with mine yet. At least nothing that has taken it out of action.
The roll pulley has had the side pop off of two of them now. The dolly grip or assistant docking wrong and it pops super easy. If the belt is aligned properly there really isn't a need for it anyway.
The other slightly annoying thing that happened was an assistant was putting away the rig and the gimbal was pushed way up the post. The plastic of the volt ended up rubbing on the knurled knob of the tilt stage and getting all scratched up. All cosmetic, but still a bummer.
Electronically and mechanically where it counts its been rock solid. And I can't imagine operating without it now. Ive been able to nail shots I couldn't have even dreamed of before.