I don't have a Delta 20, but the first thing that comes to mind is a sticking limit switch. There may be a build up of gunk on the switch that caused the plunger to jam if it was pushed in deeper than usual by the overtravel event.
You may also want to reseat the control cards in the backplane, the move may have disturbed something. Just make sure you don't disconnect any memory keep-alive batteries.
RT