These symptoms bring to mind a well-known issue in some Variax 300 guitars. It appears there can be an electrical problem with internal grounding of the main circuit board. This can sometimes be resolved by coating the internal 'coffin' with electrical shielding.
See this thread:
For more info, try searching for 'Variax 300 coffin' threads.
Thanks very much Silverhead. I've simply removed the metal coffin as the circuits seem secure in their attachment to the scratchplate. I've also sprayed all the circuits and inputs with contact cleaner spray and removed the grounding wire that attached to the wooden frame. So far, so good. The guitar was playing well last night. Tonight, I'll have it up and running for a longer period of time to see if my actions have been correct.