Some things that can make a watch gain


Watch not properly cleaned and oiled.

Oil on hairspring.

Watch is magnetized.

Hairspring coils rubbing or sticking together.

Hairspring rubbing on balance arms.

Hairspring rubbing on balance cock.

Hairspring bent out of true.

More than one coil of hairspring between regulator pins.

Hairspring pressing against one of the regulator pins.

Regulator pins bent to close and gripping hairspring.

Regulator pushed all the way to fast.

Balance timing screws loose or missing.

Balance arms bent in.