I tested this in a simple test build and had no problems with placing the stairs against an interior or exterior wall. Can you post a couple of pictures of the build you are trying to place the stairs and getting the problem?
And if you are willing to load the build to the Gallery, I or another helper will download and test it to see if I can find the problem. Just tell us the Gallery username and the name of the lot here in a reply to this thread.
Hope this helps.
Turns out I didn't remove my mods and CC, I thought I had, but it copied instead of moved. So I think that was the issue.
