Figured out the level 7 problem - the last customer only shows up if you reload the page. If you're not getting the man in the business suit as your last customer, then the level won't finish.
Not sure if this game will ever be updated, but if you do, here are some recommendations:
- More variety of stations (add a dry cleaning station, for example, instead of a 4th washer or dryer)
- Ramp up the frequency of visitors to increase difficulty
- Mute button
- Add in a feature where the machines occasionally break down, and you have to fix them
I'm about to release a small update where that will be included. Thanks for pointing it out