Follow up.
I'm still quite convinced that the SSD did not fail from heat, as the temps in the drive section of the case are hanging around 86-90F. But, I did discover that the CPU fan had basically stopped working. According to the HW monitor, the fan was running at full speed but visual checks of it showed the blades barely turning. The end result of this was that I found out why they call it shadow "baking" - the Proc hit 203F before I shut it down.
I ended up replacing the stock fan with a Corsair H80i V2. This solved the heat issue, allowing no more than 151F, which used to be temp that TrainSimulator runs at. But this cooler is massive, and even with a HAF 932 case it's a tight fit.
A look inside the VRC Locomotive Creation Factory.

