Ok...
The reel
Main gear
Pinion gear
Main gear and pinion.
Drive shaft in lock
The drive shaft has to turn to engage the reel. It will throw the lock.
I have been looking at this all wrong...
The only way that the drive shaft will engage on this reel is if the pinion turns when the reel is locked or if i turn the drive shaft.
The only way the pinion will turn is if the spool is lined up so the pins on the spool lock into the pinion.
Now if the pinion was not coming back far enough it would lock on you during a cast, a dirty spool bearing or spool shaft might turn but it would also have to be sticking with the pinion. A bent spool shaft could cause enough pressure that during a slow release of line it might bind up catching both the spool and the pinion...