The fix appears to nicely asking the forgetful unreliable agent to please (very closely pretty please!) follow the deploy instructions (and also please never hallucinate or mess up, because statistics tells us an entity with no long term memory and no incentive to get everything right will do the job right 99.99999999% of the time, which is good enough to run an eshop) not deploy too often per hour.

With one simple instruction the system (99.9999% of the time) gains the handy property that “only” two processes end up with the database files open at once.

Thanks for the vibes!