OK Micael, it actually sounds like the same issue is the possible problem for you as well. I have been digging thru git and found one very recent commit which was by Wouter.
Most importantly this fixes a file descriptor leak when checking lock dir permissions.
Please see my edit in my above post for links. Apparently core is running a patched version of nrjavaserial. As of Apr 8, there should be a fix. What versions is everyone running?
So to summarize, this is not a Zwave binding issue. Nor is it a Aeotec Gen5 stick issue. Modbus binding users are having problems as well. Please see this post by ssalonen in Mar 2021 which include links to other discussions concerning nrjavaserial
Please be aware of known issues with serial devices with openhab3 (regression in serial library used by openhab) Serial ports getting blocked after some re-connecting · Issue #1842 · openhab/openhab-core · GitHub . See also discussion in Modbus Binding not working on OH3 . I am not aware that this would be any better in 3.0.1 unfortunately
Edit:
OK I finally found the thread about running an alternate serial library. Wouter has written a patch and some users have used it to cure the problems they were having
https://community.openhab.org/t/oh3-x-alternative-java-serial-provider/128462