After a Windows (automated) Update the problem is back... 1 (random) GPU drops hashrate after like 30 seconds the miner is running. sgminer and avermore both latestversion have the same problem.
Anyone an idea how solve this?
I had one GPU do the same thing. It was the temperature of that GPU. Limiting the power in Afterburner also lowered the temperature limit.
So I increased the temp limit (and power since they were related) 5 degrees above where it was hitting.