That is odd as I have not gotten any stuck sims in apartments. Granted I haven't played this world too terribly long since testing it for the update - in which I never got sims stuck then either. The circular stairs are a problem in all worlds that is easily fixed by the user and is a programming issue EA caused with one of their updates that most of us are used to fixing. Usually all it takes is picking up the stair and putting them back into the same place - 9 times out of 10 and for the 10 thing if that doesn't fix it, removing walls or rails at the top of the stairs will definitely fix them. It is a fact if you use circular stairs they always need adjusted by the user no matter how many times a creator tries to fix them, installing the world makes everything shift to the right slightly and throws the world off kilter. You only have to look at terraine painted areas to see the shift visibly. So that is a flaw in the installation process, not something any creator has been able to overcome and only EA could possibly fix. But it was originally from a patch after LN that throws the world off - like elevators can also be a nightmare because of it, but users can fix their own worlds because the creator cannot make them do something the game makes fixing them permanently pretty much impossible.
I also will never delete any sim in the world as the sims leave an imprint that will eventually corrupt the world. Deleting them technically just makes them invisible - their files still exist and the game still counts them as being there and issues command of them. So all you are doing is putting a potential bit of corruption in your world when you delete a sims. Granted the mods - awesome and Twallans do make it least likely to leave as big an imprint, but the fact it leaves any is bad as it does not get rid of the AI the game makes when it makes that NPC for your world. Without the mods though just deleting any sims is simply setting that world up for failure in usually not the so distant future. The fact I have a few save files that that never had any sims deleted that still run perfectly and one has 26 generations of Goths and Crumplebottoms tells me it is possible to play a world forever - except for the fact you run out of room. To me that is the biggest downfall - but anyway I haven't yet had that stuck sim problem in this world. I did try it with just Winter to see how it looked and handled in snow. Looked fantastic and played fantastic, but I only played a sims week as i was trying all the world I have that I wanted to set just to winter as you need that setting in the save in order to have just one season like that, so I perhaps did not play it long enough to get stuck sims. My stairs of course were already fixed when I installed the final on this I did play for about 2 months sim time. It is always the first thing I do in a final in every world I keep is check the elevators and spiral stairs every where I recall them being.
But I guess I need to play longer. I could do that today as the world I am helping test right now won't have a new testing version until tomorrow - so I will keep my eyes open, but this world was playing smooth as silk a couple days ago. So off to this world....
