Hi,
Very hard to see where the problem could be. I have mostly used threads, but notice there you need to do an AttachCurrentThread() to get the JVM access. Not completely sure why you don’t seem to need that here (try!). See for example: Python wrapper and orekit.initVM()
Not sure if different java versions could have an influence, I typically use openjdk 8 which is what is installed with the default conda orekit.