maybe the rig can't handle 6 gpu, the motherboard maybe, or the gpu is throttling? can you check if yes with the power consumption or the usage?
I'd like to assume it that way, but I think this sometimes happens randomly?
If the rig can't handle gpu, it should happen to some other cards when I switching the riser or pci slot right? I will try that asap.
What are possible causes for GPU throttling? probably the temp? Now every card is running below 60c. Also the last time this happened to my old rig the cards were all same and brand new, the overclocking was also the same as well as all the stat reported same temperature, only that a single gpu didn't fully perform
I reinstalled the driver, seems like it is not fixed.