I would start by checking the rest of the peripherals (you mentioned having another pi - use that with the exact existing setup) That should let you know if the original board is faulty or not
If the board is randomly shutting down I suspect it will need replacing
Alright, I'll try that later today. Yeah I also figured it needed replacing.
Just thinking of how to prevent a repeat, could a split-second power outage have caused the Pi to die? While I was playing on it weeks ago, there was a quick power outage a week ago during a thunderstorm, not long enough for the PI to lose power or immediately cause this problem, but maybe that could have fried the electronics? Maybe I need to use a UPS or regulator