Well only other thing I could possible think of would be something hindering the diff’s performance such as seized wheel bearings or brakes and its putting more strain onto the diff perhaps ? So when you beat on it, its heating up ?
I don’t really know what to say man as its differentially an odd situation. I’d assume it wouldn’t be an angle issue since the Diff can only sit in the Subframe one way so I doubt it could get jammed causing stress to the pinon etc ?
I’ve never heard of Solid Bushings ruining a Diff thou and this is the 1st time I’m reading anything along those lines. Most people either love them or hate them based on the ride/feel but never heard of them doing damage so it could just be coincidence and both Diffs were already on their way out.