If your application of window film caused a window to break due to thermal stress the wrong film for your window and environment was used. Films will cause some of the solar energy to be absorbed into the window unit. If this absorption rate is too high, it can cause a thermal stress fracture.
Professionals have guidelines from the various film manufacturers to let them know what films are safe depending upon the situation. Altitude, summer maximum temperatures, shading on the window and the type of glass are all additional factors that affect which films are safe. Professionally installed films offer a warranty against thermal stress failure that covers the cost of your window replacement.
It is unfortunate that you had a problem, that is why warranties exist. Nothing is perfect as you know and I am sure that every now and then their is a problem with one of your products that you warranty for your clients. I would urge you to contact the manufacturer of the film you used, they may offer a warranty for the DIY install.
Please feel free to contact me, I will be more than happy to help you track down information for a warranty claim. We install film on thousands of windows each year without incident and have happy clients with protected views!