EF: Breakers and buss appear to be overheating on a long-term basis

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Breakers and buss appear to be overheating on a long-term basis

My 125A/240V service meter-main/load center is about ten years old, an Eaton MBE1224B125BTS, which (aside from the main common-trip 125A pair) has 12 buss lugs available. Mainly it's used for light residential loads. But since I also do some hobby-level shop fabrication metal work, I run a 50A common-trip for a large air-compressor. Due to lack of slots in those days, I cheated a bit by ganging that load with an EWH that draws 20A, just measured with clamp-on. The compressor draws 25A per leg, according to my measurement this AM. The heater is on a timer and runs in the late afternoon, and the air-compressor is of course intermittent based on my usage and having it on to begin with. So total 45A on that 50A breaker seems to be the worst-case, yes?

I have a second 50A common-trip that's used on relatively rare occasions for a plasma-cutter or a welder, both of which present varying loads, and are really very-rarely used.

Finally, I had a 20A common-trip that was, until recently, used to charge our EV (15A max) - maybe a year old. I just pulled that one last night, and found that it had smoky brown deposits on one of the two female slots. (photo shows it and the 50A breaker)

I've replaced 50A breakers three times now - not sure what they were feeding when they failed. Last night and on at least one prior occasion, it was the compressor/heater breaker. When I tried to pry it out of the bus last night, it fell apart at the buss slot, leaving the female/springy part on the buss (photo), and releasing a bunch of cracked black case-plastic into the panel. Similar thing happened on two other occasions, though I can't swear whether it was the same load combination.

The bussing itself now looks like something from a fire-inspector's training manual (photo). The black plastic insulator is warped and melted in numerous locations, corresponding to where I've hopscotched around in years past, looking for clean metal without...

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