How to repair rear brake caliper Toyota Auris / Corolla

Toyota Auris 2.0 Diesel 2006-2014 The rear brake caliper was not working anymore. I changed the piston. However the problem from this brake caliper is not that the piston is fixed, but the axel from the handbrake is fixed. The only thing that has to be done is cleaning the brake caliper with brake cleaner and spray penetrating oil between the handbrake lever and caliper.