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...
Ideas
I'm having an issue where my sims keep preferring the sink and trash bin in their business instead of the sink and trash can in their home. Their business is on floor 1, their residential kitchen is on floor 2. A sim will eat their dinner and then do their dishes all the way downstairs instead of using the kitchen sink that's in the same room that they are in. It's the same with the trash can. They will never use the kitchen trash can, only the one in the small business downstairs.
I've assigned the sinks as kitchen vs bathroom to ensure appropriate use. This didn't work though.
I use MCCC and UI Cheats Extension, both are updated to their most current form and my game is fully updated.
