Looking for advice on a problem with a NIB MMR with a low number of plays...

Issue Summary: Left flipper is intermittently weak. Can be fine for a game, just weak for one shot during a game, multiple times during a game, or not work at all for a shot during a game.
Observed: Doesn't seem to ever happen if you press both flipper buttons at the same time.

Details:

During the nice summer months, our MMR sat idle. We just recently started playing it again in preparation for the heavy use of the holidays. After a few plays, an intermittent weakness in the left flipper was apparent. We opened up the game and noticed that the left flipper spring was more stretched out than the right and the cap screws for the flipper stop assembly were loose and the stop assembly was no longer flush to the coil. I tightened them and this seemed to work for a bit, then the left flipper seemed to intermittently decline again. Opened up the machine, and it was loose again. Tightened again a bit tighter. This seemed to help and got us through the Thanksgiving weekend, but it still had intermittent weakness.

Looked on-line and found the post noting that some of the flipper link assemblies (plungers) were just a bit too long. Bought a new one and installed it (didn't seem any different in length from original). Also installed a new spring. Played a bit and still had the intermittent problem.

Then, I switched the left and right Opto Flipper Assemblies. No effect. The left flipper is still intermittently weak.

Anyone have any ideas as to what to try next?

Thanks.

Thanks for the super fast reply Lloyd. Tried your suggestion, but it did not resolve the problem. I also noticed:
- a few times pressing the right flipper button would cause the left flipper to move as well (either fully or a slight vibration)
- the left switch mounting bracket holes for the switch are not parallel to the playfield. They angle the switch a bit outward from the playfield.

Suggestion on what to try next?

Thank you for the suggestion. However, I think I did that before I posted this thread:

Then, I switched the left and right Opto Flipper Assemblies. No effect. The left flipper is still intermittently weak.

Or, maybe you are suggesting I switch something other than the Opto Flipper Assemblies?