This issue has been going on for over 2 years now and quick books online cant find any software developer to actually fix the issue?  For a company of your size this is probably one of the most pathetic things Ive ever read.  You blame the customer for your error...you have us refresh clear data and restart...it is a simple programming thing...so why dont you find someone with a high school level of programming and fix it...because it is as simple as 1 2 3

Sure you can add a sub total...but if that is your way to fix it ... then make it a standard when using service dates.

FIGURE IT OUT PEOPLE before you loose more clients because you cant make a product that is even a quarter as good as your desktop version.