50 M used as a drive motor for a submersible pump. No more than 2500 psi. We use rapeseed oil as the fluid. Have used 25M,35M, and 45M for years with similar failures but not to the level of the 50M. 50M fails about 50-75% of the time. obviously we ceased using it.
Wear pattern on springs indicates some apparent bowing of the spring causing excessive wear on one side. Wear sppears to be causing martensite formation and cracking which leads to spring failure. If spring is found broken but still in the holder,there is no wear on the faces or inner part of the cam ring.