Wouldn't be surprised if it was a ice chuck that wounded it.
The tunnel icing gets pretty bad on Nytro's and if you don't clear out the bigger chuncks and or thaw the sled between rides its very common to break stuff.
Heat exchangers have been torn away, punctured, wheels and other platic parts broken...sometimes the sled won't even go forward initially.
Always best to clear the ice chuchks and reverse the sled 1st before trying to go forward...U will be surprised at the amount and size of ice chunk(s) that will conveyor belt out of the tunnel when doing this!!
Retarded design that lets the spring escape towards the track when the retainer fails???? It should not only be held above the bolt but also in a position that if the retainer fails the spring rests on the bolt....Polaris has it right here.