Dan Winterland explained the symtoms of an unlocked primer to me once and I NB'd it for future information..... It wasn't something I'd heard about before.
A couple of years later, one of my a/c was snagged for rough running. The FI had aborted the trip. As soon as I climbed into the a/c I tried the primer.....
....it was unlocked. When resecured, the engine ran perfectly happily.
Because we don't run a 'blame culture' or embarrass people with patronising tech log entries, we made sure that all our members learned from the incident - since then there have been no further instances.
Thanks, Dan!