rizkat Hmmm... a few questions and things you can try...
- Are you on PC, Mac, or Console?
- Did you ever have Mods or CC?
- Have you tried closing the game and running a game repair?
- Have you tried with various stairs and various railing combos? If memory serves I think some stairs or rails may not have all of the options (or at least didn't initially)? For instance, had a staircase on the lot I'm building on currently that didn't show the ability to drag the bottom width out initially, but I experimented and started with a new staircase of the same type in the yard and it did have the option, so I replaced the other one with it.
- Have you also experimented on a different, empty lot and in the yard away from other things - on an open area - with the staircase/railing combos?
I would love to hear your results of trying these things, and to see some screenshots of your issue, what staircase and railing you are using, etc.