I'm using this AiO on my i7-9700k and have run into a thermal issue when overclocking. I have the AiO installed in a Corsair Crystal 570X Mirror Black case in a push/pull config. With the radiator fans, I have 3 fans pulling air into the case and 3 fans exhausting air. I keep it very cool in my house (around 68 F) and idle temps are good at 28C. The PC can be seen here https://pcpartpicker.com/b/xvGG3C.
When overclocking, I set the CPU clock to 5ghz and upped the CPU voltage to 1.30. When I ran Prime95, 4 of the workers immediately failed. I went back and stepped up the voltage until I got to 1.33 but was still running into failed workers. So I lowered the clock to 4.9ghz and left the voltage at 1.33. None of the workers failed this time, but my CPU temp got up to 90 degrees after 5 minutes and then the system crashed. I know the AiO should keep the CPU cooler than that, especially since it idles 28 degrees. I'm not sure if I lost the silicone lottery or there is an issue with my cooler.
I used the stock thermal paste that came pre-applied to the CPU block. There's no way my CPU temps should be shooting up to 90C or higher under load with this cooler. I bought it new and have only had it running since the end of February. Could there be a problem with the cooler?