I did a bunch of things, like install a VPN and a system monitor and also clicked on 'Software Update' which downloaded and installed about 250MB of updates. Now it is running Armbian 22.08.4 Focal.
Not sure if installing the 250 MB was the best idea. A shitload of things could be installed now that interfere with the miner.
You also didn't mention what settings (mode, fan settings) you are running the miner with.