It certainly does sound like you're loosing powe

If you have a voltmeter you can measure the 12VDC power lines. Just put your black lead into the back of any of the power connectors with a black wire and the red meter lead into the back of any power connector with a yellow wire. You should measure >12.0 VDC. Just leave the leads in and keep an eye on the voltage shown on the meter. You can set the meter to measure the minimum voltage if that feature is available.

Let it run until it shuts off, then see if the 12V power supply voltage dropped at any time below 12.0 V.

If it did. You can try to run the miner with two of the three hash boards powered. Just remove all 3 of the power connectors from one of the hash boards and try again.

If you don't have a voltmeter, now is the time to go get one.