I know, it's really horrible. 100% of restaurant visit I need to reset the chef in order for him to actually step in the restaurant and do what he is payed for.
The guests won't stay seated because they, for some unknown reason, have the urge to put away the dishes. But that is what the waiters are for.
Why aren't they doing their job? Why do people eat out? So they don't have to cook and clean up afterwards, no?
Other thing is sims always cancel eating their meal once they finished their drink. I hate wasting food and money. Unfortunatelly, DO is really broken.