I also am having this issue, but I disagree that it is caused by the new traits from Parenthood DLC.
The Sims in multiple save files also constantly stop what they are doing to wash dishes in random sinks (sometimes the nearest; sometimes the distance is irrelevant) when there are no dishes to be washed in the inventory or on the lot. This occurs mostly at venues where there is a Social Event or in one of the Get To Work expansion careers, but also happens at home lots and all venues. I have gone as far as clearing the inventory completely, but it still triggers. It starts by popping up to be a queued action, cancelling out the queued actions sometimes, and the Sim traveling to the sink to either stand at the sink 'twitching' with the action trying to queue or the Sim realizing that they don't need to wash dishes and they do indeed have to go fulfill a need and forget about the transgression entirely (but abruptly returning later). The Sims all have different traits and most of my Sims haven't aged up from Teen to YA to get any traits from the new pack.