Quoted from smoothbore19:
Question? After about 40 plays my upper left flipper has started to stay in the up position after a flip. It will come down if I hit the right flipper button or double left button. I have checked the coil and mounting under the flipper but all seem well. Any ideas?
Check the coil sleeve and stop. Most likely slop or mushrooming in the cool stop or dirty sleeve. Assuming you bought used as 40 plays total on the game would be super early for either of those.
If not that check the tolerance between flipper on bushing going through the PC. Should be a credit card difference.