@Kai it looks like the openHAB nrjavaserial fork had a commit which disabled lock files.
See also this comment by @cvanorman before the fork was used.
It doesn’t look like the official nrjavaserial code contains these changes.
We started using the offical nrjavaserial release again around July 15th.
There is another community thread about these lock file issues before these lock files were disabled in the OH fork.