Boom_Stick25

So happy you found the cause.
I was a bit curious how this would turn out..
Mistakes happen, its good it was reversable.
 
Happy Gaming M8.

N E W S F L A S H
 
i'm stupid.
 
 
 
 
GPU Fans haven't been spinning - Likely since i installed the M.2.
Fixed it, cabling came loose from a plug [As in the individual cables that lead into the plastic casing].
re-inserted the cable into the plug, plugged it back in.
 
Haven't had issue since.
 
Basically the worst coincidence i could have had, and looked in the wrong direction for a week. Also learnt that if my GPU fans dont spin up, the GPU will clock low enough to stay under 75c. So i didn't immediately realise there was an issue.
 
But yeah, fixed the cable, Fan's getting power, may have bumped the cable when installing the m.2? dunno.
 
Either way, Cheers for your help @thedangerine and @SkilledRebuilds 

First thought is TEMPS
Websites say its operating temp is 0...... to 70 (*C?)
So,.. reading reviews (disregarding dead drives for now)
 
They get HOT, and throttle HARD (not just this NVME, most do when TOO hot)
Does yours have a heatsink?
 
Critical Reviews -
https://www.amazon.com/Silicon-Power-Gen3x4-000MB-SU001TBP34A80M28AB/product-reviews/B07L6GF81L/ref=cm_cr_arp_d_viewpnt_rgt?pageNumber=1&filterByStar=critical
 
https://www.newegg.com/global/au-en/silicon-power-p34a80-1tb/p/N82E16820301395?reviews=all

This is a very probable issue. I would try monitoring the temp of it on your second screen next time you game and see if it is getting real hot. If it is overheating you can get tiny heatsinks for really cheap online, although your board should have heat spreaders for the ssd, may want to check if it's making good contact

Board comes with heatsink that has some decent thermal pads. I'll check it out tonight. Didn't think gen 3s got hot (though now I'm starting to feel stupid) so I didn't actually hook up the heatsink.
 
I'll let you know how it goes. Could be 14 hrs away