Sims Carrying Trash / Plates / Laundry / Infants Reset With Stairs / Platforms

This happens to me too. It seems in specific lots. I even did some remodeling thinking space was the issue, but it kept happening. I usually don't give sims more than one or two tasks at a time due to their add and interruptions from other household members. It happens even when they only have one task. The lot it happens the most in, and the one I've remodeled to make sure there's space at the top and the bottom of the stairs, is also a lot with platforms. No idea if that means anything.