I made some stairs and railings a few weeks ago and tested them and everything was fine, but suddenly today the railings are too long.
I've no idea why they all of a sudden would be like this, any help would be appreciated.

Another thing, when you place the stairs with the railing turned on, the EA default railing shows, don't know if that has anything to do with it.

Well getting your new railing to place instead of the default EA one, that I can help with! http://www.modthesims.info/showthread.php?t=362583

No idea if this causes that railing to extend but give it a try. Another question would be, are you sure that each step has just one small section of railing? If the top step has a longer railing than it should I can see it doing this. Are you using CFE on the lot at all?

I'm not using CFE on the house, it looks the same inside the house.

I cloned the ibeam railing and only changed the supports, in Wings it was the same size then the clone.
In workshop under the mesh tab, it has the high and low mesh plus modular 1 to 4, or 5, not sure.
When I replaced the high mesh with mine, only part of my mesh appeared, the front part still looked like the clone.
Same with the low and modular 1 and 2, I think it didn't look like my mesh until I replaced the 3 and 4 modular.
You think that could have something to do with it, I'm really not sure if I've done everything correct.

What I don't understand is that the first few times I tested it, everything worked fine.

Thanks HL for trying to help, will have a look at the link.