Tom if you know a bit about Python you can delay the shutdowns by forcing constant CPU wake-ups As soon as you login, go to to terminal type 'python' import time while True: time.sleep(0.00002) (press tab on this line first) Press enter twice. And then disable FileVault straight away If your computer is really shutting down so fast you you can't disable FileVault try plugging in all kind of devices, like an external monitor, USB mouse/keyboard/hard-drive and Thunderbolt/USB ethernet. I found that helps sometimes.

I can confirm the solution posted by sf98723 works! Do exactly as they say. Thank you so much. Just a FWIW. I don't believe it has anything to do with the graphics. It's a faulty chip in the 2013-2015 MBP that is interacting with the NHI.kext file to cause the CPU to shutdown. More details here: https:// outluch.wixsite.com/rmbp-crash

I have managed to rename/delete the NHI.kext file but it's useless because in Big Sur the kext is cached into the preboot process so it's still loaded in memory and causing crashes. Unfortunately you can't unload it and until someone tells me how to remove it from the boot kernel collection we're stuffed.

I desperately need help with this too. I have a system kext that is causing my Mac to crash always instantly. I have managed to remove the .kext file from System/Library/Extensions but the kext is still loaded in the boot kernel collection. How do I remove it from this is Big Sur? Any help is appreciated.