Solar good. Install a heavy fuse right on the positive battery post, a lot less expensive to change.
Then find the largest 12V light you can and hook it in series with the positive battery cable. It must be large enough to not light the light or very dim with the parasitic rig loads. Now push/pull the wires and plugs until you find the problem.
Plus there should be burned/arcing evidence at the short as it takes a lot of amps to cause your problem. I don't suspect your solar as 10 ga wire would become very hot, but disconnect it if suspicious.