sounds like the brake hose might be collapsed internally. fluid goes to the wheels cylinder but can not return to the master. So the brake shoes stay expanded.

With the drum off,  and shoes all connected -  LIGHTLY apply brake pedal pressure.(have an assistant do it)

You want to see both Wheel Cylinders Extend and retract fully.  Is possible the cylinder is extending but is crudded up and not able to fully retract releasing the shoes.
 
Again also = check your parking brake cable that it is Slack in the short run from the pivot quadrant to the Parking brake lever in the backing plate. If its loose + jiggly its fine.  Other issues.

   

I may need to take it back to Heritage but that requires borrowing a trailer and finding time when they are open so I'm going to try to do it myself if I can! I'm in no way blaming them, the brakes have been the best they have ever been since they did the work a year ago. So I assume correct shoes and installed correctly as they were fine. This is just a sudden change. I was parked on level ground and did not set the parking brake. Something changed from when I braked to park it to when I tried to back out later that day. could something be stuck in the brake cylinder that is not allowing it to fully seat? I played with it a little without taking it anything apart and "seemed" to be fine as both sides would slide in and out no catching. The springs are in place and seem to be fine. Will look at it again tonight. I'll compare to the other side as well.

FYI.... they're shoes....not pads 

Might the shoes be installed backwards? They have a leading and a trailing end with respect to rotation.
Are the shoes the proper width for your drums?

Compare to the side that isn't sticking.the

Also, I don't think you mentioned backing off the adjuster. If it was set to spec, or a little tight, it would make the drum hard to remove. If you applied the handbrake when the drum is hot and left it parked, it could become oval. When you release the handbrake, the drum would rotate to the narrow section and stick. If it was dragging to begin with, it would get hotter than the other side.

That's an easy one, take it back to Heritage Garage.

Thanks for the replies. I did have it jacked up, wheel off and screws out that hold the drum on. I made sure the park brake was slack. I worked fine until I parked if for just a couple hours. I didn't use the parking brake. I finally did get the drum off by prying it from all around and banging it. I inspected the parts and nothing obviously out of place. I had someone pump the brake and the pads both extended. I tried multiple times to put the drum on (partway) and spin. There is still resistance and the pads are engaging. I am not an expert by any means but I have had these apart and back together a couple times in the past. I'm currently at a loss. Any other ideas?

Zach.

Have you checked the handbrake cable? With the handbrake lever in the fully released position, you should be able to feel slack in the cable all the way to the drum backing plate. Check its routing and see that it is not seized or binding anywhere. You should also be able to pull on the cable slack and see the lever that goes into the backing plate move freely.
To remove the drum, you will probably need to slack off the adjuster and handbrake cable so the brake shoes relax their grip on the drum. There should also be two retaining screws holding the drum to the hub. Tapping with a hammer around on the drum will help it to start moving outward. The drum is often tight around the wheel studs, but once moving out to the threaded part it should be looser.

Time to get your hands dirty.  Jack mini up. Use a jack stand. Pull the wheel. You need to back off the square adjuster at the top of the backing plate. The adjuster needs to come out, not off. After a couple of turns, Take a hammer to the edge and try to knock the drum off. Go around the drum. It will come off.

Hi, I have a 67 Mini Cooper S that I was driving and seemed fine. I parked it and later that day I tried to back up and the right rear brake would not release. It was not fully locked and would roll (enough to put in the garage) but definitely still engaged. I took the wheel off and tried to pull the drum off without success. The brakes recently had a full overhaul at heritage mini in costa mesa and had been working great. New pads at that time. Any advice? Thanks

Zach