I realize that there isn't much to go on yet. I'll update this report if I catch it happening. But I've noticed that occasionally, my Sim will use a toilet in one restroom, and will then go to a sink in a different restroom (at home, this is usually on a different floor) to wash her hands.
Usually, she'll use the sink in the same restroom where the toilet is. And the sink in the original restroom seems fine, and I can make her use it to wash her hands after she's autonomously gone to the other restroom to wash her hands. It's weird that occasionally she goes to a different restroom to wash her hands.
Edit By Crinrict: Adjusted Title fit old fixed bug report
