Mid 2014 MacBook Pro 15 Random Shutdowns

So my mid2014 MBP 15" has been experiencing random shutdowns for a few weeks now.

It's an issue with the CPU, some cores can't deal with being set at a lower frequency (power saving method in macOS) and subsequently shit themselves. Screen goes black, fans spin to max and then eventually the whole system dies.

It's fixable but the fix is a bit of a pain in the ass and also removes your ability to make use of a thunderbolt ethernet adapter so use at your own risk. If you need the ethernet adapter you can use a paid solution but I can't vouch for how effective it is.

Anyway, this is how to solve the issue:

Run this in recovery mode:

csrutil disable

Restart and run this in macOS

sudo mount -uw /
mv /System/Library/Extensions/AppleThunderboltNHI.kext /System/Library/Extensions/AppleThunderboltNHI.kext.bak

Reboot into recovery mode and renable csrutil. That should solve it till you next update macOS, then ya gotta do it all over again.

Update for 2020

Looks like this fix doesn't actually solve the problem anymore, I'm still seeing random shutdowns occur with roughly the same frequency as without the fix applied. Looks like it's time for a new MBP.

2nd update for 2020

As a final hail Mary I opened up the laptop and took some compressed air to it, got loads of crap out of the fan housings and also replaced the thermal compound on the heat sink.
For whatever reason I haven't experienced a sudden shutdown since so here's to hoping I don't have to replace the old girl yet!