2 things I have found that cause this annoying problem.  First is to set the allen head bolts that push the reset bar so the far end (away from the solenoid) is slightly higher than the solenenoid end.  This makes sure all the targets lift above the lip sufficiently to lock.  Secondly sometimes hooking the spring on the other way around can sometimes make a difference! Seems sometimes the spring is 'twisting' the target and that can make it stick.

Worked like a charm, Loosened the far end, gave it a twist and tightened down. I would never have thought of doing this.