Your customers as client have MTs or some other routers!?
And if is like that every customer have an public IP.
If you set rule "connection-limit=100/32 on your AP. That means that every your customer is limited to 100 sesions! (100 sesions per host).
And if you set connection limit 50,32. You limit connections for that router to 50 sesions. That means that your customers 10 PCs is limited to 50 sesions (10PC x 10Sesions = 100 Sesions ).
Better remove that rule!
my ap is a highgainantenas 8186hpmaxx with realtek chip at 800mw and my cpe are smartbridges airpoint outdoor model
I don't what is it! But I known this. Simple divice as Pheenet 118C+ in AP mode can accept ~20 clients (CPU is small to do the job). Check how meny clients can have your AP.
Second problem can be your big power. 800mW i't general to big for city.
May be your AP make big noise (interferense) and killing him self!!!