Is it only in a specific GPU and after that all of your GPUs stop? Have you tried to remove the GPU that is stopping and test it again? Also have you tried it in another system maybe the motherboard. Still if you will not try all of the posibilites we cannot know that it is really the GPU that is the problem.
İt is not the specific GPU. This time another one stops. I start pc, control GPUs, see three of them:OK, run afterburner
everything is fine. after a while sometimes one hour sometimes a couple hours one of the GPUs stops and
the others remain running.
i also updated the windows and drivers...
Then try to change your ram, storage or motherboard as it is the as it is the only hardware that you did not troubleshoot. It can be quite a job yes but even the problem is the GPU stopping it can be other hardware really. Is there any indicator on your motherboard an may I just ask the full specs of your PC.