I see from your original post edit, you fixed the issue
A dead fan on a GPU will certainly cause issues.
Although,
generally, a BSOD isn't triggered by a GPU overheating.
Normally, the GPU BIOS will just shut off the GPU when it greatly exceeds thermals, while throttling it to a much lower performance when approaching thermal limits.
Basically, the game would start slowing down on FPS very quickly and noticeably, and then the display would shut off, sometimes with the computer also turning off/rebooting.
You mentioned in your edit that it was a GPU purchased through Aliexpress (unless I misread that??)... If so....
It is very common for sellers on that platform to provide counterfeit or "hacked BIOS" GPUs, based on much older/lower capacity GPU chips and DRAM, that are designed to trick driver packages into thinking it's a newer / higher performance GPU.
As in the card loads the drivers for and reports itself as a 1070ti, but it's hardware is actually a much older GT series or such.
A very very very common side effect of the hardware vs driver miss-match is BSODs, as that driver set will try to make calls and functionality to hardware that isn't actually present on the fake card triggering a crash and BSOD.
Because driver packages and most hardware testing program only rely on the GPU's BIOS to let them know what it is, and the fake cards have that BIOS hacked to report false information, it can be very challenging to ferret out a fake card, with the symptoms created by the hardware/driver miss-match being the only clue as to this issue.
Easiest way to determine if it is a fake 1070ti, is to remove the heat sink, wipe the thermal compound off the GPU chip, and see what model GPU die it says.
For an nVidia GTX 1070 ti, it should read:
- GP104 <-- GTX 1070
- GP104-300-A1 <-- GTX 1070 ti version
https://www.techpowerup.com/gpu-spec...-1070-ti.c3010
If your GPU die is the correct model number for the card, then all is good; Apply fresh thermal compound to the die and reassemble, thus knowing your have a real card and that you just extended it's life more and lowered it's operating temperature a bit with fresh thermal compound (that stuff does dry-out/loose capacity over time, so fresh paste every few years is a good thing)
If, however, it is a fake, then you will know and can make informed claims about the fake and/or to get it replaced.