One Circuit of Breaker goes down and comes back? Possible or Impossible?

Last week, one circuit (as connected to the breaker box) went down for 5 seconds and then came back again. Main power never went down. My understanding is that breakers don't auto-reset, ever. Circuit in question has had years of operation without such incidents, and has been working since last week with no more such behavior.

Question. Is the only explanation for what happened that someone tampered with the wiring for that circuit in the crawlspace? Or, is there some other explanation I'm not aware of? Note that no heavy load was on the circuit at that time, just a normal load - 40 watts of CFL, and a desktop PC and laptop, which were basically idling at the time. Moreover, the load didn't change between when the circuit went out and came back, and the circuit wasn't browned out, it was completely dead for 5 seconds.

Poor connection at a terminal is a strong possibility, but if you can rule that out until there is nothing else, ..........
If it's not a critical circuit I would be inclined to wait a while to see if the fault recurs.

I've had failed MCBs that were allowing 200V through, giving the impression of being dead.

No,idea. I see you are not UK based. Do US breakers reset? Just wondering

@kerching US breakers are better than that, they never trip in the first place https://www.allelectric.com/blog/2019/october/the-danger-of-federal-pacific-circuit-breaker-pa/

Is that not the ultimate ‘Bang’ test that our cousins across the water rely so much on?

Phoenix said:

@kerching US breakers are better than that, they never trip in the first place https://www.allelectric.com/blog/2019/october/the-danger-of-federal-pacific-circuit-breaker-pa/

Click to expand...

Ah, so it's their version of Wylex or Proteus then?