A lot of us use Z2s and found that the majority of issues could be solved with a few simple things. Firstly, fresh batteries (which you've already done), secondly clean the hopper right the way through, which I assume you've also already done, and finally, try cleaning the rubber band belt thingy that drives the hopper from the motor. If you get any paint, gunk, mess or anything on this, it can slip and if you have a fully loaded hopper, it simply won't drive the plate. It's pretty easy to clean, just take the shell off, turn on the hopper and lightly press a cloth/tissue against the band. Your problem sounds a little more complex than this, but it's always worth trying, at the very least to rule this out as a potential cause!