Carefully check the condition of the parking brake parts. If a cable is broken or chafed, replace it. Make sure that the sector teeth and latches are not damaged; replace damaged parts.
Check the condition of the spring. It should ensure the return of the lever to the non-working position. Check the condition of the rear cable sheath and the fastening of the lugs on the sheath, and also make sure that the cable moves freely inside the sheath. If the sheath is damaged and the fastening of the tips is loose, replace the cable.