Teracube 2e randomly powers off

I have had my teracube 2e for a few months and all has been well. Yesterday, the phone started powering off by itself. Initially, I was able to turn the phone back on as normal by holding the power button. Since then the phone has randomly powered off several times. The only way I am now able to get the phone to turn back on is by first removing the battery and then holding the power button for a minute (a trick I’ve learned in the past with another phone, which I assume drains some power still held in a capacitor somewhere). I have tried searching for solutions and the closest I’ve found was this thread → Phone automatically shuts off - #14 by adamsterk - General - Teracube Community however, I am unable to follow the steps suggested here because there seems to be no option to wipe the cache partition on e/os.

The battery has full charge, confirmed by checking with a meter.

Any suggestions?