With no inverter or generator operation, and not plugged in, there will be no AC voltage on the wires. You could extend/retract the slide with no danger of arcing. As Cal says, if you are concerned about your house batteries, running the engine provides alternator power to ensure there is adequate juice.
The only potential issue with this approach, is if running your slide in or out were to bring that "frayed wire" into permanent contact with the flange or other grounded metal instead of the temporary touching that you've experienced. If that were to occur, when you plug in, start your generator, or run the inverter, you may then apply 120-volts AC to the wire that is already in contact with ground.--creating a steady short. Under that circumstance, the circuit breaker on that particular AC circuit should open, preventing a bigger problem, but it would be a concern. Based on the intermittent arcing that you have experienced ONLY when actually moving the slide, this seems very unlikely to occur--but it would definitely be something to watch for.