Hi. I have a very similar problem that's got me stumped.
I noticed the N/S/R pads were worn right down, disc red hot so I replaced with reconditioned caliper and new pads. The OSR caliper was also stiff so I took this off the car and freed and cleaned up the mechanism. In fact, this wheel felt even stiffer to turn but had way more material left on the pads.
Now with everything back together the same problem persists, ie. NSR disc is red hot, the other side (with the old caliper back on) is just warm to the touch and seems normal.
It is NOT the handbrake as I tried temporarily disconnecting it - no difference.
The wheel turns freely with the car jacked up, both the handbrake and footbrake lock the wheel and then release immediately release it when pressure removed.
The only thing I can think is either the flexi hose has an internal tear (unlikely surely?) or that the ABS is faulty and routing maximum pressure to this wheel, though this seems unlikely too. I occasionally get the orange brake pad warning light on the dash but I drove 65 miles last night without this and the disc was still red hot. Note this is a hollow circle with no "ABS" in it and I don't use pads with wires.
I'm stumped. Any ideas anyone please?!