I have not heard of that situation but I have had the valves stick shut sometimes. It usually happens if I am going slow on the way up from a staging area to the alpine. Not able to run the engine hard enough to keep everything running clean. As soon as I opened it up in some deep pow the valves worked properly the rest of the day.
Does your sled do it all the time?
Yep i had that happen to mine, they warped enough i was leaking out the side of the seals and the bellow was in perfect shape. replaced em and fixed the problems i was having. expensive little buggers those caps are. haha