The detent, return or canceling spring is broken, missing, or out of position.

Replace the turn signal switch.

The switch mounting screws are loose.

Tighten the screws to the specified torque.

The turn signal switch is broken.

Replace the turn signal switch.

The canceling cam to canceling spring interference is uneven.

1. Inspect the canceling cam and the switch.
2. Replace the damaged parts.