I have long time struggled to get my HA installation running but now I seems to have found the cause of this. My initial plan for the HA installation was to use an Rpi4 with an USB SSD disk and with Z-Wave devices but it always failed. Somewhere along my attempts (I have done a lot of them) I found something strange, the issue with getting the Z-Wave devices added to HA was connected to using the USB disk, when trying to use an SD card then everything did work fine - so I then did the assumption that there was some problem with using USB SSD.
However this was wrong, everything did infact work quite fine except from the Z-Wave part which made me question the issue with compability. After seaching a long time I found this guide: Installing Home Assistant on a RPi 4b 8GB with SSD boot which provided the answer - the issue is not SSD disk at all (as such) but rather the comment “USB3 signal frequencies may interfere heavily with WLAN, Zigbee, ZWave, Bluetooth, enOcean!” which where the source to all my issues. So the solution was then easy: do not connect the Z-Wave stick directly to the Rpi but rather use an USB extention cable and put your Z-Wave stick far away from the Rpi!