The single explanation I could think at is that there is a message into the queue that may produce the unexpected behavior. In case you haven’t solve this case (by yourself or via support channel) you may try to start with a fresh queue (like renaming queuefolder into queue.backup+ service start) and see if the crash is not anymore present.
If the problem is still present please contact our support via dedicated channel as these kind of situations may need more investigations to be made.