90^5 / 3 / 24 / 3600 = approx. 23000 combinations/s
That rate seems much too high, for either a mechanical lock mechanism or an electronic keypad (which I guess would have some kind of lockout for brute forcing anyway).
For example a standard Master dial lock has 40 hash marks but, IIRC, older ones had only about 12 valid positions. There was a trick you could use to find the third position, which would have left 144 combinations try except there were a few invalid combinations reducing to around 120. This is for a lock that a naive estimate would but at 40^3 or 64,000 combinations.
Or as others said, the lock mechanism could be faulty or seized.
No idea if that's a common problem with safes, but it's pretty clear that a safe would not have any outside maintenance access to fix a problem like that (other than drilling it open, which seems to be routine enough given the "yeah, we can make it usable again" offer)
2. It's a trap lock and was never designed to be operable in the first place.