Passenger rear brake won't bleed QV Coupe

First great off great Mondial resource and page. I have been using this site it's a great. Taking the car out of storage ( QV coupe )so far has been more work than usual. Car started right up but wouldn't go into gear. Replaced the slave cylinder now shifts and runs no issue but I noticed my passenger front brake was dragging so I decided to bleed all four wheels. I have a motive and a mityvac. Passenger rear wouldn't bleed so for yucks I bled the other three working my way back to the master with no issue. Then I went back to passenger rear. I have fine pedal pressure btw. Still no joy. Took the bleed nipple all the way out, junk in the nipple hole, cleaned it, i was thrilled to find what I thought was the issue, put it back in, still no juice. I loosened the flex hose at the brake put the motive at about 7 pounds pressure and it wept at the hose thread so I think the lines are good. Any thoughts on what to try next ???

 

There was junk in the bleed nipple but I cleaned it out so could be some upstream? I even took a piece of piano wire into both the nipple and the hole it goes in used a mallet to tap the rear of the brake housing. But I agree the caliper may be it. That was my next target I was just hoping I might have overlooked a bit. I'll start taking it apart. I have never done that before any advise is appreciated. I have the shop manual but pics are always good as well. Thanks!!!!

 

Ok thanks!!!!