Why does the breading always come off of my oven fried chicken?
The longer you let the flour/breadcrumb mixture set on the chicken before cooking, the more the gluten network will set up, which will improve adherence to the meat, as well as make the breading stay intact as a shell. The issue is that when you cook the meat, the breading and meat expand at different rates and are pulled apart. A longer set time will make the breading hold up better. Also make sure you're baking on silicone mats or parchment paper. Any amount of sticking to the pan will make the coating peel off - non-stick pans are great, but nothing is non-stick like parchment paper is, for baking.

I'd recommend trying to bread the chicken then let it sit in the fridge overnight so the gluten network can set up more. If your breadcrumbs get soggy try doing the egg wash and bread crumbs as the very last step - apply the buttermilk, flour, let it sit, then add the egg wash and bread crumbs just before baking.