Thanks, everyone! I have totally forgotten about the 2:16 delay thing.
Most of the time, after plugging in the PI30 and connecting the power cable, I would go about doing other set up chores before entering the TT to turn on the A/C or other appliances. That takes a lot longer than 2 minutes. For the couple occasions that I described above, I think I probably had entered the TT right away after plugging in the PI30 (yes, it is a portable one) and cable trying to turn on something and found out that there's no power. Hopefully, that's what it was. I will definitely check this out the next time when I am out there camping.
I might also get one of these polarity testers. It appears to be a very handy item to have around as an additional insurance thing or for checking against the PI30.
S.K.