I had an 850W power supply and started getting random complete PC power off’s during flights. The situation got worse where I couldn’t even start MSFS without it occurring. It never occurred running any other software.
Replaced the PSU with a 1000w unit and it hasn’t occurred since.
If your PC suddenly shuts down it’s unlikely to be any software bug but the overload protection in the PSU tripping out.
MSFS certainly causes spikes in load and seems to cause trips even when a PSU is supposedly rated sufficiently for your PC.
My advice would be replace the PSU with a higher spec unit.