PS4 freezing not HDD related

my PS4 is freezing and i am not sure whats the main cause. i have replaced the HDD, but that did not solve the issue. i have opened it to clean fan and heat sink that worked for a week and then it started happening again. i dont use it to play games just for my streaming apps. not sure what it is it will freeze randomly out of the blue. what do you thinkis the problem?

Seen one came in freeze as well even with new HDD, likely CPU related.

thanks so you think if i maybe add new thermopaste that may hlp as it could be the cpu overheating ?