Graphical issues. Not rendering textures. Overheating

Hi.

I have had a very loud PS4 pro for about a year. I decided to replace the thermal paste after experiencing graphical issues. I have cleaned it all out replaced the paste with thermal grizzly and new thermal pads. Still have the issues. It's running really hot. Fan is quiet now but not controlling consistently. I have moved games to an external HDD to see if it was a corrupted drive after re initializing PS4. Not sure if it's an issue with GPU or ram. Games don't crash, just get slight issues with edging on walls and houses. Also have issues with a delay of up to 5 or 6 seconds on rendering textures which is why I tried a different HDD. Any help would be most appreciated.

Regards Steve