No Mods. Fresh install..(stopped playing for Fallout 4)..Gifted to me. This is from a previous comment I made.
Hello All,
My dear old mother snuck this GP on me and I have told her I didn't like Sims 4....but she is nearing 80 and I am not about to refuse her gift..
I tested this little GP. I ran a diner for 5 days. I did not run long days. I praised, trained, and promoted my staff (for a hamburger style diner, I knew I would not be making serious money so my character I loaded up money. The service of the hired help gave me no issues (have not run into them being culled yet). As I made sure the staff was taken care of, so far they have not failed on their own accord.
The worst problem is the customers and they stop the Diner from running great or even good. They are all over the place chatting, standing, using their cellphones, bugging other customers, or just standing. The standing is an attempt for them to try and do the musical chairs. They seriously mess up the flow of the diner.
Here is a minor one.. the ones in customes are my staff..Everyone has been seated.

And again..all these customers have been seated.

All customers have been seated and other customers that ate hang around interrupting customers and staff.

Again Repeated

And another..The host(Witch costume) is blocking the view of the guy eating his delivered food at Goth's table and they did not come together.

This is horrible. Even if I have been lucky with a great staff and culling them are sneaking up on me..The customers are terrible.
I found if you give your Sim the neat trait you can help clean dishes (heh helps when your waiters and waitress are busy).
Also it appears Host/ess like setting people outside if you have an area and guests do too. And I have mostly enlarged cheap items in the one diner above and made them huge..I get great décor from customers.
Oddly I have yet had only staff use the restrooms ..XD
I keep my diner open 7 to 8 hours and never have staff complain they are tired..
Do not know if this helps anyone.