RF brake locked up. Why?

Ok then;
firstly, the driver's side is the left side
Brake fluid on the underside of the hood can only come from something in the engine compartment. If you have applied and released the brake with the M/C cover off,as you would do during the bleeding procedure, the returning fluid can easily gush thru the Compensating ports, and squirt up to the underside of the hood, even with the hood open.And then it drips down all over everything. Such a high fountain usually only occurs if the brakes were not yet properly adjusted.... or if there is air in the system. After you have stroked the pedal to make it hard, air in the system can be compressed to 800 or more psi. It has become a high pressure air-spring. Then when you lift off she unloads and forces all the fluid you just pumped down the line,back up into the M/C, with predictable results. Once the shoes are adjusted and the air is purged, very little fluid movement is required, and the returning fluid usually only roils in the bottom, with perhaps a lil fountain.

The photo appears to be of the passenger (right) side, and looks to be correct except the shoes should have two different length linings on them; a long and a short; the difference being about 2 inches; and the long one goes on the rear side or to the left when looking at that passenger side system.
Your self-adjuster cable appears to be a lil short. After it is installed, the blade should be resting on the star wheel, ready to crank it down, which should lengthen the adjuster. This event should only happen when backing up, as the entire shoe assembly is cranked around by the dragging drum. Since the cable is anchored at the top,the blade is forced to flick the starwheel. If the shoes are already properly adjusted,then there is insufficient cranking of the assembly to make an adjustment.

The pistons in the wc,have to retract after every application, to allow the linings to properly rest fully against that top anchorpin, so they cannot drag on the drum. If the fluid is not returning to the M/C, for whatever reason, then the linings may not retract far enough to not drag.
If, simultaneously, there was to be an air pocket trapped in the wc, the dragging shoes could, I suppose, heat that pocket enough to expand the air to act like an air-spring, and keep the shoes applied, maybe even increase the drag, in a vicious cycle.
If there was water in there, it would be even worse.
Silicon fluid is not hydroscopic, so any water in there will settle to the lowest point..... which is the wc.
Brakefluid should always be used from a sealed container.
I don't think any of these is your problem; just suggesting the possibility.

Next; as to points #1 and 2
You have to prove that the piston inside the M/C is properly parking, to the rear, so that the fluid can return. From the previous discussion, I think your C-ports are fine, but here is the procedure to prove it;
There are two ways to do this; directly and indirectly.
Since the drum is off, you can try the indirect method.
Make sure the reservoir cap is installed and clamped shut.
Make sure only one drum is off.
Have a helper step on the brake pedal, while you observe the shoes moving out. Ask your helper to stop about half-way down, and then lift off. Those two upper springs in the assembly; (OK WAIT! I don't see the lower spring in there. There should be a spring just above the star adjuster, holding the two shoes together. I assumed it was in the shadows, but I just can't see it; So make sure it's in there), should immediately start to smoothly retract the shoes, back onto the anchor. This proves the fluid is returning,and that the wc's are not sticking . Repeat several times. This also proves any valving in the system,or the distribution block, are also passing fluid... so yur done testing. This would indicate that hydraulically, the system is functioning properly. This does NOT prove the hoses are 100% as at this time, there is no pressure in the system with the one drum off.

As to mechanicals;
Make sure each side has a long and a short lining on it. and that the short one faces the front of the car on both sides. Drum brakes are self-energizing, and the rear shoe does most of the work, so needs to be longer. Well actually, the cheapazz manufactures can save some coin by making the fronts shorter,lol. If you don't have shorts, then as long as all 4 front linings are about the same length then it will be fine.
Make sure your wheel bearing endplay is properly adjusted. If it's loose, the the chassis will move down from it's normal attitude and could force the shoes into contact with the drum. I know it's only a couple of thou when properly adjusted, and then it's no big deal. IIRC endplay is maybe max .007. With drums I run them fairly close to zero.
Make sure the pads on the backing plates where the metal shoes rest are smooth, so the shoes slide smoothly over them. You can put a tiny dab of hi-temp grease on those flat pads to reduce wear. If the pads have ruts/ridges in/on them, grind the high part off. If deep, you can build it up.
Make sure the metal part of the shoes do not rub on the drum, or the step that often wears into the corner down in the bottom of the drum..
Make sure, on a dual-reservoir M/C that it is correctly plumbed. the front-most reservoir on the factory system should go to the rear wheels.
The first inch or less of pedal travel, can be non-functional, as the piston in the M/C is moving out and closing the compensating ports; this is normal.Make sure the pedal returns to the top of it's stroke by itself and rests on the stopper. If you flick your foot off the pedal in the first inch of it's travel, the pedal should sorta snap back to it's parked position and make a satisfying lil thud.

And above all, make sure you have a hard pedal, and that it gets hard in the first 50% or so of it's travel, and that it remains hard with modest pressure for at least 20 seconds, and that it never suddenly drops down.


IDK, that should cover it.
Happy Hunting