So I bought an AMD build from them, and usually the CPU fan should be screwed into the motherboard, so it applies maximum pressure.
Anyway, I decided that I was going to change the CPU fan and I was trying to unscrew the existing AMD cpu fan and I couldn't figure out why the screws weren't changing pressure. Turns out, that they weren't screwed in at all! In fact, they had no ability to be screwed in, either because the computer was missing parts (possibly the case was really crappy), or the motherboard was incompatible with the CPU fan. I was shocked.
Probably worth checking your own build to see if the CPU fan is actually screwed into the motherboard. Otherwise, the thermal paste is literally the only thing holding it together.