Intermittent issues and things like this are where engineers earn there salt.
Being experienced you generally have an instinct of what it maybe from the environment or system log and then you can use your tools to see if you can confirm this (multimeter tests, reproducing the issue etc)
When it's down to placement problems you would minimise this at installation time, steel wouldn't be of a concern from a false activation POV but could reduce signal to the panel, you can check for this tho.
As an installer coming out to the job if all the tests were inconclusive you would likely just swap it, as a return visit would cost more to the company then a passive and battery. Doing nothing would help no-one here.
It's a different situation for yourself, I would be thinking about re-siting it with a new battery initially. Other tests you could do is to mask it off completely proving that it's not detecting something in the room or swapping it with another room.
Plenty of options and things to try to pin it down, but what we would do is probably different.