I work at an older sawmill with a lot of open wire trays leading to PLC cabinets, we would have to burn down the place and start from scratch to seal all the holes. And mice, cats, ants come with the territory(plus deer across the road in the field, which a couple of our employees got in trouble for shooting at from the lumber stacker).
This isn't my first time with a rodent story. When I was in the Navy, on an aircraft carrier, a rat climbed into the main shore power transformer for half the piers on the base. Killed power for a couple of hours, and we had to run our emergency diesel generators till shore power was restored.
What sucked about that was it happen just prior to duty section change(I was off going). When we lost power the ship went into security alert and the oncoming duty section could not come aboard.