The drop target in front of the lock stays up at times it should be down (for example at the start of a game or after multiball), so the locks are harder than the settings intend. Both its coils fire in solenoid test.

Lock drop target stays up: the drop-down bracket is bent

Cause: The bracket that the knock-down coil pushes on bends out of position over time, so the coil fires but no longer releases the target. With standard settings the target starts down and only comes up during multiball.

Checks

• In solenoid test, watch whether the knock-down coil actually drops the target, not only whether it fires.
• Check the target's down switch in switch test.
• Check the lock difficulty setting before assuming a fault.

Fix

• Bend or adjust the bracket so the knock-down coil releases the target reliably.
• If it keeps going out of adjustment, replace the bent bracket piece rather than the whole assembly.

Systems

• WPC Fliptronics

Games

• Fish Tales

Source: Pinball Repair help group!! (Facebook group)