The max upgraded version of the "straight tower square" has 2 doors on the floor, which are inside of walls placed next to them, and 1 door on the actual level of the max upgraded walls (but not on the other side of the tower)

The round tower circle doors get bugged.. and sometimes you have a door and a window.. on the same wall

EDIT
No matter what, all towers will only have 1 door on them, both corner and straight towers.
max upgraded with max upgraded walls, only 1 side will have a wall.. dedicated a small island to testing this. no matter what order of building or placement

edit 2
The door placement on stone corner towers is terribly misaligned no matter how you place them, however saving and reloading the same save fixed missing doors

https://imgur.com/a/uu8c3z4