I've said it, Reno said it again, I'll say it again...
"The "burning hot spot" says it all. Kill it NOW!The two cans should NOT be carrying current! This is NOT a time to be collecting data in a situation like this. A high/low voltage problem is indicative of a lost neutral, and should not be left in this manner for any amount of time...
We can not go troubleshoot it for you, but it is obvious that the neutral is gone! And it sounds like a second connection of the grounded conductors (Neutrals) to the ground(s) of the sub-panel.
I hope your liability insurance is top notch.... The joint could be on fire right now, some items react that way with the voltages you've described.
Heres a simular
example . Ignore the roaches and needle containers, focus on what happens when a ground becomes a current carrier, and choosing paths on its own.
