One thing I did notice is that during the boot the red LED on the Pi was coming on and off which I havent seen before. It normally stays on permantently after power on.
The red LED must be permanently on. If it's going off it means you have a power supply problem which you need to solve first - if the power isn't stable the RPi won't run stable and it could well be that the odd crashes you are seeing are caused by that.
Disconnect all USB peripherals and everything else you might have attached (fans, HATs etc) and make sure everything's working fine. I also strongly recommend using the official RPi power supply as that's known to work just fine.
so long,
Hias