No--it's not common---at least at the factory that Toplace uses. I've seen a problem with it at the factory that we use only once. And that was with a special design that had poly 'fingers' that
extended from 3" to touch the front hairline. I had only seen that design twice before. Normally a customer orders 3/4" poly on the back and sides. We've never had a problem with this standard design. It's only when the design gets 'tricky' that this could become an issue. Did your poly go around the entire unit including the front, back and sides? Where there any 'fingers'?