The flipper stays up after the button is released.

Flipper sticks in the up position

Cause: Worn rubber on the pawl where it meets the EOS switch, catching on (and fraying) the EOS blade; the bat too tight in its bushing; a broken or missing return spring; or welded cabinet switch contacts.

Checks

• Check the pawl and EOS blade.
• The bat should have about 1/32" of vertical gap; no play means it is too tight.
• Check the return spring.
• Check the cabinet switch contacts are not fused.

Fix

• Replace worn parts, reset the gap, fit a spring, or separate and file (or replace) the cabinet switch contacts.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Flipper button sticks
• Flipper fuse blows
• Where flipper power comes from
• Measure a flipper coil
• Flippers dead after long storage: corroded button and EOS contacts
• How flipper power is routed by generation
• Three flipper mechanism generations
• Most flipper faults are EOS switch faults

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)