Title says it all. My sims can't use modular stairs. They'll try to go up or down them, and then jump like they've been reset. But guess what? I don't an object error, so I can't use NixPick's "What Caused This" to even find out what's causing it! Any ideas? I'll provide a mod list if anyone needs it.

Edit: Alright, so I dredged up my mods using Delphy’s Download Organizer (I temporarily swapped out my Sims 2 download folder with the Pets one to scan the right one) and narrowed it down to the mods that effect routing. I stumbled across a few ghost mods I thought I had deleted, and there was a group that stuck out the most: MidgeTheTree’s Playable Ghosts. Her mods don’t seem to work well in the Stories series unfortunately. So add that to the list of probably incompatible mods. Fooey. https://midgethetree.tumblr.com/pos...en-i-thought-id
So I tested the game without it, and my sims seem to be able to use the modular stairs now. Hopefully it’s fixed. Thanks for the help, Simsample!

backup your game and test without your mods. Does it still happen?

Well, I know one of my mods is causing it, but I’m struggling to narrow down which one. At least, I hope the game isn’t broken...

But I’ll let you know.

Try the 50/50 method:
Game Help:Finding Problem Custom Content^wiki

Just to check, you are playing Pet Stories?

Yes. Also, I decided to narrow down my search. I knew that it was a mod that effects locomotion. I’ll edit my main post to show you what I did. Thanks for quickly getting back to me!

Oh good, well done for fixing it! It's always tricky to find mods compatible with the stories versions.

Oh yes, I know. My method is throw stuff at the wall (game) until it sticks.

Generally Lifestories is OFB, Pet stories is Pets and Castaway stories is Seasons, but they have so much of those games hidden that's it's hard to be sure what will work. So your method is probably the only good one!