This may be really old hat, and it may not work for everybody, but I think I`ve found a workaround to fix the issue where sims can walk up but not walk down spiral staircases (since Pets and the last patch, or the last patch and Pets?). I say I think I`ve found a workaround, but I found a thread over at MTS which linked to another thread and it was there I found a post offering a solution which seems to have sorted the issue for me.
Okay, I tried the method where you add the finished lot containing the spiral staircase to your lot bin in game, then in EIG add the lot last of all without doing anything else in EIG, saving, then exiting EIG. This method didn`t work for me, sims still couldn`t walk down the spiral stairs. My spiral staircases tend to be against walls, and in some cases the lot was built around the fact spiral stairs were used. I didn`t really want to rebuild the lots to accommodate normal stairs or redesign the interior to move the spiral stairs away from the wall, although, I was resigned to doing so. A tad frustrating. Okay, I admit, tears were shed

The solution.
Remove any fences or half walls at the top of the spiral staircase. At least, remove any fence or half-wall where the side rail rises up above floor level. It worked for me, and I didn`t have to move the stairs or turn them to any different angles. Happy happy joy joy.
I test exported, and in-game, without altering my spiral staircases in any way, sims can now happily walk up and down the three sets of spiral stairs in my world

Again, don`t slap me around the face and neck if this is already common knowledge. I`m just happy at the moment and needed to purge the joy.
Comments
But it is good to see it work in other houses and that this is the actual solution without having to reset the whole lot or worse - enter each house and rebuild it. UGHHHH. Labor no one needs.
So thanks Johnny for confirming that. I was not positive, so I sort of didn't say much about it.
Yeah Regina, I read about that on the other site. My heart pained for her - just the thought!
"Games Are Not The Place To Tell Stories, Games Are Meant To Let People Tell Their Own Stories"...Will Wright.
In dreams - I LIVE!
In REALITY, I simply exist.....
Sorry Reg, didn`t see your post. I do hope this works for all those spiral staircase sufferers of late. I was a bit scared to post in case this was all a bit last month`s old news. But`s it`s cool, I`m a happy bunny.
Edited to correct brain fog surrounding the name of Johnnywr's WIP... :oops:
Where are we going, and why am I in this hand basket?!