Since the moment I have finished watching Brett Kollman's vid on Trubisky, I can't "unsee" him not following throw with his hips, when he throws. Every time he doesn't, he easily misses his target. I don't know what else the Bears/Nagy can do, besides sitting him and Dave Ragone down, forcing them to watch Kollman's vid, and bluntly telling Mitch "fix this now... get your shit together."
As others have already stated, you have to stop babying him now. It's doing more harm, than good. He either learns to deal with the rough crowd, like the one that roasted Cutler weekly, or he fucking folds like a napkin.