Soooo apparently, some sapphire cards have some sort of mounting pressure problems. This means that after a certain thermal paste replacement ( two or three times ? Mines 3 and my friend's two ) the card mounting pressure is screwed up and it made the card overheat increasingly, eventually death by overheat arrives. I'd love to have a clear insight about what went wrong but I don't have a lot of sapphire cards at disposal. By far here are some of the examples that I have discovered.
Exhibit A ( My RX560 ) : I was having a quite good temp ( high 50 to mid 60 ) with the stock stuff. After my decision to replace the thermal paste the card hit 72 instantly and slowly rose to oblivion. My method of application: X, star, youtuber pattern, pea, line basically anything imaginable and the amount vary from too much to just enough. I've spent total of 20$ in thermal paste which is mx4, kryonaut.
Exhibit B ( my friends RX570 ) : My friend was having a decent 74°C with same story and his card reached high 80s while he had spent the same amount of thermal paste as I did and he used the same mx4 and kryonaut and the only diffrence is he applied enough to cover the die which is quite excessive as to people standard.
Tl;dr: seems like some sapphire polaris cards have issue with temperature after thermal paste replacement and it seems like it has something to do with pressure