That's not good
Having belt modded my EQ6, I have a better (than nothing!) understanding of how my mount works. There's not a lot to them...the handset talks to the motor board, the motor board tells the motors what to do, the gears turn, and assuming the clutches are engaged, the mount turns.
With the standard gears in the mount, I don't see how they could randomly slip, as they are meshed together. Unless of course they are no longer meshed. Likewise the worm gear. Still, might be worth checking the worm gears are adequately meshed all the same. If you haven't already, checkout Astro Baby's mount guide
http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm
Puzzled
