Sims Reset and Cancel Actions When Using Stairs

Lately, I've been experiencing an annoying issue when playing in two-story houses and other lots (I haven't tested it in buildings with more than two floors yet).

Whenever my Sim is upstairs and I tell them to do something downstairs, they obviously need to use the stairs to get there. However, just as they start walking down the stairs, or right before they do, they suddenly appear downstairs, their queued action gets canceled, and the game seems to reset their position.

As a result, I have to select the action all over again, which gets really frustrating, especially when it happens repeatedly.

Has anyone else experienced this issue? Does anyone know what might be causing it or how to fix it?