Folks,
A caveat on the following comment --- I have not had time to read all the posts, or the preliminary reports or reports of same, maybe the point has already been covered.
It is a long time since I was on the B767, but I clearly remember that there was a particular type of "trip free" Cb used on some systems which could only be reset with power to the circuit removed.
With one of this type of Cb, pushing in a "popped" Cb then looked like a Cb that was set/reset, but wasn't, a potential "gotcha".
Tootle pip!!