I would suspect that your ground prong connection was damaged in the receptacle, explaining the dim hot to ground indicator. Moving the meter probe around inside could have caused a hot to ground fault, nailing one meter lead. Once the arc struck, the ionized air could've involved the other meter lead. I haven't had it happen to me. Do you recall if the tester had a snug or a sloppy fit in the receptacle?
I don't recall if the tester was loose in the receptacle.
I haven't finished the basic work of going through all the receptacles yet. After the incident with the meter I found a couple more receptacles where the tester gave the same indication regarding the noticeable difference in the indicator lights. I didn't use my meter to test those receptacles since I don't have a 3rd set of leads - haha. Once the initial investigation is done I will have to go back and take a closer look.
Besides the mystery with burnt leads I found an interesting pattern with a run of several receptacles, all in the vertical position, where the top plug tested good and the bottom plug was inconsistent. Inconsistent in that the tester didn't always indicate power in the bottom receptacle until after a second or third attempt or sometimes the right hand indicator light would flicker which, if only one light is showing (left hand side) it means a short to ground. I assume it has to do with the receptacle contacts wearing out but if that's the case why the bottom more so than the top? All receptacles in this parkade are typical duplex style and are shared by two parking spaces and therefore the top and bottom receptacles should wear fairly evenly. Who knows, maybe it's the guy using the tester that's the problem...
Initially I thought this job was going to be mind-numbingly boring but instead it has given me a couple things to think about.