Hi , I think your only option is to remove the rotor to confirm what is going on. This is quite straight forward, remove the[ 2x bolts 17mm socket size] which hold the caliper to the upright. If you twist the caliper side to side this will push back the pads and pistons which will allow the caliper to slide off the rotor.Now locate the allen screw in the centre of the rotor clean out the hexagon and tap in a good qaulity 5mm allen socket and carefully remove the allen screw without rounding the hexagon.
The rotor may now be removed by carefully pulling and rotating the rotor at the same time. You can now examine the parkbrake there should be two long springs which pull the shoes togeather and two curly springs which hold the shoes to the backplate.The hold down springs have a hook which passes through a slot in the backplate and then by turning the spring through 45 degrees it hooks onto the backplate. The springs are removed by pushing in the centre with needle nose pliers to compress the spring and then turning the spring through 45 degrees to release the spring from the backplate. The parkbrake shoes can now be carefully removed if needed.
If you are in any doubt of the condition of the parkbrake shoes , cables , rotors and brake pads then fit new because all these parts are inexpensive.
Examine the adjuster which is at one end of the shoes and determine which way the threaded stepped wheel is turned to reduce or increase the length of the adjuster, once the rotor is fitted the adjuster can be accessed through one of the lug bolt holes and the shoes adjusted untill they just clear the roptor.
Before refitting the caliper check the brake pads are free to move in the caliper, make sure the caliper bolts are tight and pump the brake pedal a few times to reset the pads . Check the operation of the park brake with the car still lifted, now do it all again on the other side!
I hope this helps it really is easier to do than to write about if in doubt just shout Cheers Linds Cornwall UK