I agree that it sounds like the environment. You best bet is if you can catch the pattern and be in the room at the same time as a reset to document exactly what occurs. Mainly looking for any of your power supply lights to go out or certain cards that go busy. One other thing you may try is to power down the system and reseat all of the cards to make sure there is a good connection. I have had issues with Techs screwing the cabinet down too tight and the backplane being off wack.