I don't have a good answer but it seems once an RV has had mice even if you get rid of them it seems to attract more mice. I would at least try to find out where their access point is. Remember a lot of wires also go from walls into the ceiling which would make me believe that you could have mice all over your RV. I would probably look into a professional exterminator.
Mice truly are nasty vermin.
Tom Marty
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