@eno: I was able to reproduce the issue on High Sierra, Mojave and Monterey but ONLY on Java 17.
On Java 8 , all three tested OS worked fine.
And latest update did fix it for me on all tested OS.
Have you changed theme on your JDownloader installation ? Settings->Advanced Settings->GraphicalUserInterfaceSettings.lookandfeeltheme is default?
Can you please check with newer java, see
https://jdownloader.org/jdownloader2