Are they busting before you start the thaw process or during it? I learned the hard wash that when I began to unfreeze a bay i would start with the wand, work up the hose, to the boom, etc. I busted fittings that way because I believe the tip on the wand didn't provide enough of an opening for a rapid thaw and the ice would have no where to go.
t have since learned to remove the hose/wand from the boom and put it in the equipment room to thaw. I then start working the boom on up. Of course my freeze ups now are far and few between as I've tweaked settings in the bays over the years.
I have always taken off as many hoses as possible after a freeze up and let them thaw in the ER. At the wash with the busted fittings, I don't know that they are busted until it thaws on it's own, but I'm sure they bust upon freezing.