Hello,
The board might have an issue or it really is CPU related.
Check the CPU socket pins, mis-aligned or bent pin can cause issues.
Uneven pressure distribution with your cooler mounting bracket, take it off and tighten in the correct sequence.
[1][4]
[3][2]
1,2,3,4 = screws, slowly turn in the order shown, do not fully tighten a screw. All must be done progressively.
Also there is an ECO button on the board, not sure what it does but is could alter the CPU voltages / frequency.