That's really not too unusual as Donnie said the smaller they are the thinner skinned they are and either having the water too hot or not starting with warm water to do the initial thaw like I do and then I take their water temp up a level to hotter so they don't fast thaw.
Still depends on the size of the feeder but really hot water makes a mess of that thin skin sometimes.
Trust me they will still go after it myself I used to toss the feeder out if it broke open at all but the snakes don't have an issue with it just a bit more blood and gore LOL
