My suggestion is similar to Jim's if I'm following. That said, the first thing I would do is measure the carcass and drawer to see if anything is out of square, particularly front-to-back of the cabinet. You can get away with less than 1/16" and adjust with the tabs that exist on most slides, but after that, you're going to have issues. I've not personally experienced your issue so perhaps post a picture so we can better understand the problem.