Funny enough this upgrade caused a loop for me, until i also upgraded the firmware, now resolved.
Also as mentioned HAp lite is on the ragged edge of space, i had a backup on it and it could not upgrade until removed.
Its seems this DMZ actually does what it saysYou mean there is another router (provide by ISP?) before the mikrotik? If so see if that router can set to "bridge mode"
sometime DMZ won't solve double nat problem