[OPEN] [SE] Sims get stuck/crash when group hiking at Senbamachi

I am having the same issues as listed by others. It seems to be linked to group hiking. Sims can hike as expected on their own, but when in a group (2 YA, 1 C), they stand at the top of the stairs and the game will eventually crash.

EDIT: It seems that the issue is due to the stairs. I had a family (same as before) do a hike on the mountain and it was going fine. But when they use stairs in the world, that's when they bunch up and things go wrong again.