Ah I see ha ha I'm a HGV mechanic by trade. I love cars, had a few micras now. Been wanting to build a 2.0t micra for years now. Finally doing it, just want some extra stopping power on the back.
the rear caliper handbrake mech are prone to the lever seals getting old, drying out the grease and end up seized/sticking.
grab the lever with pliers and swing it fully, you should see the piston nudge in/out. if the lever or piston gets stuck, the lever or threaded shaft mechanism or the mount inside the piston has prob dried up n needs overhauling.
its not for the fail hearted or impatient and will be fiddly but do-able if careful.
imo the rear disc handbrake and perhaps also the hydraulic braking strength is pretty poor compared to drums but good for withstanding high speed track abuse.