Pitch-Locked Props on PW100
 

It appears that this malfunction has caused several non-fatal ATR accidents. It also appears that until recently, there was not much information about this sort of malfunction, at least in the ATR manuals(may have changed). Therefore, I suggest reading this incident report about it. Like many accidents, there were other issues involved but it would be useful to be aware of a this possibility and its ramifications.....

Air transportation safety investigation report A20C0107 - Transportation Safety Board of Canada (tsb.gc.ca)