Which bug deflector do you have? The ones I see available do not have much of a "wing" to change the wind. They look more like a chip guard for the hood.
It has to be a design/material flaw. I have 3 mavericks in my company. Not counting fixing chips we have replaced 7 windshields. We have tried both oem and aftermarket, no difference. We run smaller sedans, jettas, etc. We do not have problems with them. My personal one which is about 1.5...