Thanks for your quick answers. I do not run any other software besides Photolab that uses the GPU and for this test I did not use any accelerator software. As soon as I start Photolab GPU load goes to 100% in AMDs Radeon Performance Monitor. Watt usage goes up to around 40 Watt and stays there no matter what I do. Even if I close Photolab. I also used ProcessExplorer to check if I could see a task still running but I didnt see anything obvious.
However, I think I found an answer and a workaround for now: I am also seeing the same problems described in this thread: PL4 with AMD RX580: Save has Failed Internal Error (Correction failed on the execute stage) - #19 by John-M
I reverted back to AMD driver version 21.2.3 (had 21.8.2 before) and this solves the problem. GPU load is still at 100% and Watt at 40 when using Photolab but it goes back to normal when I close it. I can live with that.
So I guess its a problem with the driver version as others have also expirenced. Right now I can live with the older version and I hope the next driver version from AMD or the next Photolab version will fix this issue.