I've been having this issue as well. If a sim already has a owned business ( B&H) or one in their household the game can't cope. It wants to keep sims on the lot. Sims won't go to work or school. They start and stop until the icon turns red and doesn't react at all anymore.
One of the sims also has a job as a criminal, and when they made a promotion it also gave me a pop up about her being promoted at her small business. Which she is the only person employed at.
There's 3 small businesses on this lot ( as advertised it shouldn't be an issue) and 5 sims. One is a child and he can't go to school. 2 are on 1 business, the other 2 also have a business. The mom also has the side job, which she can't go to. Unless you leave the lot. Certainly when the small business is open all the sims on the lot will want to do the customer actions. You don't have this with the retail lot of Get to Work btw. If I start them on other activities they nearly always cancel midway. It's incredibly annoying.