I think they only run everywhere if they have a high amount of "Active" points. If you either create a sim with less points or, use a mod (such as the
Multi-Painting by Merola) to adjust the DNA/Genetics of a Sim, that might work as well.
I also just spotted this answer by oblivio in
THIS thread: "If you turn on boolprop testingcheatsenabled true, and shift-click on a staircase, you can choose how your sims walk, i.e. walk angry, walk sad, run, etc. I've used this for sim movies, maybe you can use it to make your sim walk again. Also, I think the stair have to be the shorter porch steps, but I'm not sure. "
Cheers!