I am also having this issue, only at the Medina Studios apartment.
The dogs haven’t been able to go downstairs alone for a while now, I’ve had to leash them and “go downstairs” together and command them to go potty.
I can’t even do that now, and my sims won’t go alone either.
It started this sim morning - last sim night, it was working fine as I have my sims walk their dogs every morning and evening. When the parents got back from their walk, I had the two teen sisters travel to the karaoke bar. I sent the younger sister home, and traveled with the older sister to her boyfriend’s house (old salt house). She got home around 5am... it’s now 8:15am and I am trying to direct the younger teen sister to walk the dog and she can’t. I also tried sending her downstairs and she won’t go alone.
There IS a trash plant outside near the door, and because of its location I cannot dispose of it, even with cheats. It’s been there for a while now, and it’s never been “in the way” of them using the elevator before (I had this issue at a different apartment before, and it was because 2 trash plants were blocking the stairs to the door - I used cheats that time to make their evolution stage “withered” and they can be disposed of, and that fixed the problem). The plant is off to the side a bit so it’s not directly blocking the doorway, but it’s technically on the ground floor of the apartment lot so when I try to dispose of it, they give me the “can’t go there” bubble.
I do play with mods/CC, and I haven’t added anything new between the time it was working and when it stopped, which again was maybe 8-10 sim hours.
It’s the beginning of summer, so harvestfest hasn’t been and won’t be for a while now... no other recent holidays either - I play on long season settings.
I don’t know what is causing this but I can say it’s super annoying... if all the CL elevators are going to slowly break, that kind of makes the apartments irrelevant and I really love playing in the apartments/San Myshuno.
Thankfully I was already planning on moving this family to Windenburg after their new baby ages up, as the parents own a bakery there already and they need more room for the new family member - I just didn’t think I’d have to go through all the work to move them so soon (I play on long lifespan so there’s still like a week until baby Diego ages up into a toddler). 😏