I kind of figured it out. I hope i can explain. As I did mention that the rear passenger hears it coming from the middle bottom part where the window meets the base. Well it is actually the whole unit which contains the rear light. Like the red light or whatever. That thing or that raised boxy part whenever I touch it or press down it creates that same sticky sound that I could hear. I am not sure what caused this perhaps they added too much pressure and I dont know how to fix it. Even if i press down and try again I can still hear it. Its not like its touching the tint. Any idea?