Hi,
Have you located a schematic for the PSU yet? if not, that would be the first step.
"while the right side is stuck at 49.9v (on a 30v unit) "
This sounds like output transistors E-C shorting. You are seeing the full supply voltage, none regulated, at the output terminals. Check those. ( usually something like 2n3055's or 2n3773's etc).. If not, then go further back to the regulator circuit itself.
Presumably, the PSU has no 'crow bar' protection to clamp over voltage.
Hope that helps.