To me, this is not at all like the problem described in the original post. In fact, I don’t see any evidence of the problem that you describe. I’m not saying it isn’t happening, but not evident in the message log posted.
The first restart is caused by an exception in the sampler. That is rare but possible given that you have been unplugging the AC adapter.
The next four restarts were caused by heap memory depletion. This is a problem that is always caused by WiFi issues. You RSSI looks good, but there can be other issues that cause it like other devices using the 2.4MHz band (there are many) or a misbehaving device using the same band or router issues. Nothing I can do about that. Would be interested in when that started as it might give a clue to the cause.
The last restart, what I think you are talking about, is a power fail restart. It looks as though the unit was not running from 2/15 at 13:34 until 2/18 at 00:18. That’s 2 1/2 days.
Your unit appears to be about 3.5 years old. While I can’t point to any particular issue from the past, my gut tells me its the SDcard. Try replacing that and see if the problem goes away.