The issue is that the zips do not provide enough amps to the bit motors.
Couple of suggestions: All are at your own risk
1)search the message board for PCB Mods
2)buy a cheap clone with the same freq as your zip and swap the pcb's (check that it works with zip controller first)
3) Go get a microsizer.
The PCB swap is my favorite worked great for me.
Hope this helps.
