My sims either won't follow a command (just stand there) or they "do" it without actually moving. For example, they will go to sleep without getting into bed. I've linked to a video to better explain...
Ideas
I have this issue too since one of the more recent updates/packs my sims will complete whatever tasks I set them without actually moving, sometimes they even go to work while also being visible on the home lot. The portrait fades out like they are at work and I can change things on it like work hard etc..... or if I tell them to eat or shower or whatever their hunger/hygiene will go up as if eating or showering while they are still standing where they were. I have all packs/expansions/kits and have never used mods or CC
Edited to just add I have tried repairing my game several times.
What platform are you on ?