Issue is still ongoing with latest patch.
I originally thought it only happened when a lot was initially loaded during a session and doors would stay "fixed" during the same session but I have experienced doors I "fix" during a session will again bug out. For example, I had to fix a bedroom door so a sim could go to bed, fast forward through sleep time, and door was again bugged when that sim woke up. I have had Sims walk into bathrooms and get stuck because between entering the room and relieving themselves the door bugs. I even tried a fresh save, started playing Johnny Zest--first time I have ever loaded that particular lot, and one of his doors bugged out within the first half hour of play. I replaced that door, quit the game and restarted my PC, then did a quick and dirty starter home with only a front door and bathroom door and minimal furnishing to keep item count low and moved in a freshly created sim.
That house lasted almost an hour before the bathroom door bugged. That sim never left their lot the entire time. I replaced the door (completely different style door) and quit after verifying it worked. I played only that household the next day for a couple of hours and replaced that bathroom door twice more.
While no particular door style seems more or less prone to fail, it only seems to happen to internal doorways. At no time have I experienced a door on an external wall fail. My two room/two door test house had the same, cheap base game door for entry and loo initially when it first failed. I replaced only the bathroom door with one of the two tile wide doors that should be an external door and it failed. My final session with that house and save involved adding a bunch of different doors to the external walls and another room and the room door and loo door both failed twice in a couple of hours of play--external doors always seemed to work fine (this was the only time I utilized door locks and only on some external doors)
I did most of my testing with base game doors but Cottage Living doors are also susceptible.
It is not cc/mods
It is not a corrupt save issue
It is not an age of save or duration of play issue
It is not a "too many objects" or "too full neighborhood"
It is not a particular pack bug creep
It is not number or frequency of Sims using a particular door
It is not a pre-made versus simmer-made building issue
It does not appear to be a particular door(s) but it may have something to do with external and internal walls.
The only thing I have not tested--since I normally get paid to bug test, is whether how rooms are built plays a part. Particular doorways, no matter how many times I change out their doors, seem more prone to fail. The little upstairs loo in the Caliente starting home failed often no matter the save although all internal doors for that house have bugged out at some point in play. One of my builds had four internal rooms with each having a door and three failed multiple times during play. The one door that did not--again, that cheapest base game door, was the only one of the four built using the contiguous wall tool rather than the room tool.
No, the latest patch did not fix the issue.