It doesn’t make sense to test on port 53 if you are failing to test 5335. Because nothing else AGH will do. To ask Unbound running on 5335.
You performed the test of Unbound on the system hosting Unbound? Just to be sure 
Can you do a reboot and check unbound logs afterwards
journalctl -u unbound
Did you have done any configuration changes to Unbound? e.g. activating some other features like DoT?