Unexpected switch to battery when plugged in

My librem was left plugged in. When I came back a few hours later, the display showed it was running on battery power, which was down to 40%. I unplugged it, and plugged it back in, and it is now recharging the battery.
We do get a lot of power outages, but there was nothing that affected any other electronics during that time.
Any ideas or suggestions as to what could have happened to make it “lose” power?

I had a very similar situation recently, though it is unlikely you have the same issue.

The problem for me turned out to be an intermittent open in the AC cord running to my power supply. I verified this issue with a multimeter while moving the AC cord, checking both continuity and output levels. I was not hard on this cord at all, so this was a bit of a suprising result.

Purism replaced the entire thing, though I really only needed a new cord with those three, circular “pins.” That connector seemed solid. Fortunately, it was not the DC plug on the system itself!

Maybe first you can try moving your AC adapter around to see if it “disconnects” and “reconnects.”

Thanks for the suggestions: I tried wiggling and moving all the cords, and nothing happened - until a minute later, and bingo back on battery. I will contact tech support.