Hey Edward, thanks for your reply and suggestion. I wouldn’t be surprised if it turns out to be corroded contacts, the camera is old enough for that. Would be a cheap fix, I may give it a try.

The on-off stuff seems simply like a bad (corroded?) electrical contact… I would blow some electric contact cleaner in there. WD-40 makes some and markets it everywhere, but I would recommend the CRC stuff as a more professional (and less likely to be mistaken) alternative – it is even food-safe(!).