In my humble opinion it sounds like he's just feeling good and lacking ground manners. I had the same thing happen with my Qh's. I didn't have much of an issue when they were haltered and on lead...They would basically do what I asked. But, at liberty or having to catch them would often times be a Pain in the butt. ( I walked softly but carried a *medium sized stick ) Literally, I carried a stick, Never did I have to use it other than to just poke them in the butt once or twice to get them to move over. I would try carrying a crop of your choice ( I really just used a stick). Think of it as an extension of your arm to help direct the horse and keep him where you need him. Placing it on his chest and requesting him to back works great, mine didn't like the stick touching them and eventually, I didn't have to carry it. I would always use a verbal command along with a regular command. Never did I allow "gate rushing" I would wait outside the gate until they were bored with me or would back up like gentlemen.
Time and Patience... Keep a cool head and if what you are doing isn't working, it's because the horse doesn't understand the cue or command. I try to keep every thing as simple as possible. EHHT! Means no, I don't like that. BACK! Is just that. Back up. I probably say those two things the most besides ( I love you and you're a goooood boy..lol
You're safety is #1. Keep that in mind and I wish you the very best of luck!