Encountered this as well.
Two bobas left on the counter is enough to block sims from ordering.
I haven't seen the issue with food orders. Sims usually retrieve their food properly.
Sometimes after ordering the boba they order food. They take the food but not the boba (sometimes they drop it on the floor to retrieve the food).
I've only seen this happen on the ThrifTea lot. I have traveled to the Pier but haven't noticed the issue.
I have also seen that it depends on what day/time it is. ThrifTea has events (fashion show event for example) that affect townie autonomy.
If there's no event going on they seem more eager to swarm the boba counter
It is also happening in my game. I can barely see the options active to buy a food / drink…
