Sorry Blue, I missed that last post.
Chkdsk inexplicably started working again after its inexplicable stoppage with no input from me, no errors when I run it. I hadn't heard of that fdisk /mbr before but after googling it I can't imagine it'd do anything that formatting and starting again wouldn't have also done? Because that didn't solve anything.
I've just sent in a massively long warranty request in telling them all about the problem and that I have no actual proof it's the SSD and that I can't even reproduce the error with any regularity.. I dunno, maybe they'll be feeling charitable.
Edit: Got the standard "send it in" response. So I guess I'll be getting it replaced.
BorisBC wrote:Pro tip - if you have to spew in a car, spew down the (inside) front of your shirt. Trust me, it's a lot easier to clean spew off yourself than the interior of a car.