The King vassal penalty was supposed to be fixed in a recent update. But your issue sounds like a different matter, as it was applied to any king vassal you had.
Are you updated to the latest version? What version and checksum do you have? Should be 2.1.4 (XQSJ). If you do, screenshot or save games would be good to see what is going on.
Are you updated to the latest version? What version and checksum do you have? Should be 2.1.4 (XQSJ). If you do, screenshot or save games would be good to see what is going on.