My apologies, for not more clearly pointing out that I'm running headless, in a thread focused on GUI, as well as jumping the gun without prior confirmation. Just as you suspected the issue at hand is not due to FileBot but my underlying system. Further digging following the information gathered ...

Thank you for your response :) I must start by admitting that I might have jumped the gun on this one. I first started to experience the issue after upgrading from FileBot 4.7.9 to 4.8.2. Found this thread which error description matched my situation. Upgraded to the mentioned beta version 4.8.5 ...

Hi, new to the forum, fan of the FileBot function :) Have encountered the issue of FileBot freezing my server, FileBot 4.8.2 headless on Ubuntu 18.04. Have since updated to the available beta release 4.8.5 (r6064), I can confirm that it too contains the bug. I'm using Java SE Runtime Environment 11 ...