@crinrict I did some experimenting with this and found some interesting results. First off let me just say I only have access to base game locations, the only pack I have is Kids Room (because it was free with Game Pass) so I can't test other places. Also before I get into what I found, let me also just say that I personally could only replicate this at The Solar Flare. I could not get the same results on any other lot, and I tested all pre-existing base game community lots and several residential lots. To be more specific about my game version, it's 1.60.25.2300 and I'm using an Xbox One X.
So after reading what MzMelonz said I tried to see if my active sims would do the same thing, and they do. So basically any sim (inactive sims included) trying to leave the lot by means of walking off of it has a chance to glitch when trying to use the stairs. As mentioned already one possible result is that they walk down and then reset, cancelling out the interaction to leave, but that's not the only result I found. Sometimes sims just bypass the stairs altogether, and just basically teleport down somewhere in the vicinity of them while also cancelling out the interaction to leave. I've noticed a lot of sims will get to the bottom of the stairs then stop for a few seconds before continuing on, though this doesn't seem to cancel anything. I saw several inactive sims walk downstairs, stop, walk back upstairs, stop again, then finally walk back down and leave.
I also did some experiments with the building and lot. I first tried deleting the stairs and replacing them with different ones, didn't help. I then flipped the stairs around in a 180 degree rotation to see if that would help, nope. I tried to completely delete that entry room at the bottom of the stairs, nope. I tried replacing the stairs with the classic wooden ladder, and I didn't notice any issues. I also tried going into my library and placing that version of The Solar Flare over the existing one, didn't help. I then took that same version from the library and placed it on a different and empty lot, no problems. With that attempt I noticed sims were using the door off to the side of the stairs, so out of curiosity I went back to the default location for The Solar Flare and tried another experiment. I removed the door facing the road, forcing sims to use that one to the side of the stairs, and I didn't notice any problems. I also tried replacing The Solar Flare with a different type of community lot, the gym with the big staircase (Movers & Shakers), and had no issues.
I'm not sure how helpful any of this could be, though I figured I would share it since the results seem pretty weird to me. OH, almost forgot. I also experimented many many times to see if it would happen just by commanding a sim to go down the stairs, and the only time it would happen was when using the Go Home interaction.
@crinrict Admittedly I don't remember trying that with my initial testing, though I did go back and try it and it was still happening. I even noticed a result which I didn't see before, though it only happened once so it may just be something else. What happened was my sim apparently reset at the top of the stairs before even going down, and I say apparently because I got so used to the problem happening at the bottom that I was on the lowest level keeping an eye out there. When I moved up a level, however, my sim was standing right near the top of the stairs and also had the Go Home interaction cancelled.
One other thing I didn't think to do last time was to expand the ground floor entryway towards the front of the lot, so I made it even with the upper floor and now I'm seeing another interesting thing happening. Now there are times where a sim reaches the bottom of the stairs and just disappears as if that was the exit point out of the area. This is only happening to inactive sims, my played sim doesn't seem to be having that happen and so far I'm also not seeing any resetting going on either.
I did also remove the multiple floors completely, and moved everything on the upper floor to the ground floor. Obviously it fixed the issue, but I'm sure that doesn't help figure out what the problem is lol.
@MzMelonz I don't mean this to seek sympathy or anything, and I'm certainly not using it as a way to mock others in a similar situation, but I simply don't have a life and I'm not in a very good place overall so for me being able do things like that are great ways to distract myself and get my mind in a better place even if just temporarily. It certainly wasn't very fun sitting for who knows how long and watching characters walk downstairs, but hey if it can potentially help anyone and also get my mind of off the crappy things then as Beavis and Butt-Head used to say... "we're there dude" lol. Plus listening to music as I experimented helped significantly.
I do think I need to try more experiments now though. When I replaced The Solar Flare with the gym I also switched the lot type to a gym, so I think I need to test just changing the lot type to see whether or not the lot type does actually impact things in any way. One other thing I feel I should test is in regards to when I tried moving The Solar Flare to an empty lot. In it's default location I tested whether or not the sims would glitch when they only had the side door to use, but when I tried moving the place to the empty lot sims were only using the side door and I didn't test the front one.
