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

[Pants]

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 the smoked insulation. Evidently there's enough heat generated to leave a damp-looking brown sooty deposit around the blades in those locations, but the distorted half-melted plastic is really what stands out.

Now, I'd have given up on this and just replaced the load-center, but this is a unitized meter-can/breaker panel. I'd be at risk with the local electrical utility if I were to go pulling the meter out (and I'd be working live, which I'd prefer not to do) to replace the whole nasty affair. So I'd much rather replace the bussing - separately.

Through an unbelievably bureaucratic process that took around a month, I got in touch with the right POCs at Eaton. I was thinking they're big enough that they'd just send me the damned replacement bus, and would perhaps share with me whether there had been such problems reported with some of them. Nothing like that happened. No, they require that I

• buy the new bus from one of their local distributors
• return the damaged one to the same distributor
• that distributor then has to UPS the damaged part to them in Illinois or wherever - can't come from me
• IF - and only if - Eaton inspects and then agrees that there was some problem that they're responsible for, they will credit the local distributor for the UPS charge, and separately refund me what I paid for the replacement part.

It's BYZANTINE. Since none of the local distributors wanted to take any of this risk on (understandably), they declined to get the replacement part for me.

But I'm really not sure that this is a defect, and if so, whether it might just as well be with the CH breakers (or whatever I've gotten to replace them in the past.) If they're passing more current than they, or the bussing, can handle without the drama, then why don't they ever trip?

Am I breaking a standard rule in terms of derating for my loads?