You might want to check the voltage at the flippers. The playfield power goes through the tilt relay so make sure that it is clean.

This L bracket adjustment will work on any Gottlieb before 1976 with the older flipper mechs. Makes the machines a lot more fun. It can also be done on the newer ones with 2 inch upper flippers as they are running the old mechs.

You also increase your stroke and target spread. I do that on all the pre 1976 Gottlieb pins.