I bought a used T7600 Dell without a GPU. I did the following:

Installed an MSI Geforce 1080 GPU
Installed an SSD
Installed windows 10 pro

From the getgo, I have been getting the clock watchdog error after the PC has been running with a relatively heavy load (python data science) for 10 minutes to an hour. I have tried the following:

Installed all possible DELL drivers
Installed the NVIDIA drivers
Passed the Intel CPU diagnostics
Ran Furmark GPU stress test with no problems
Ran DELL stress tests on CPU, RAM, GPU with no problems
swapped out RAM with some new RAM
put in a new PSU
reinstalled windows

all to no avail

I am ready to get a replacement motherboard as a last resort but I am at wit's end. Any help would be appreciated. Thanks.