On SMOS, I set the target temperature to 75°C. For overclocking, I'm trying, 1050 Core, 1950 Memory and 950 Core undervolt.
So I changed Core undervolt from 900 to 950. It still doing the same thing.

The cards work fine when plugged into a monitor.

<<But what about the plug I suggested?
Did you try?

If you don't have this plug, you can connect to another monitor, another TV, just to see if works >>