This post may be better served somewhere else, but I thought I would chime in. My TB's history is unknown to me, he is 17 and pretty much been there done that or so I was told. He is calm, sensitive, and willing but if he gets nervous he backs up. I haven't experienced this much til I went off property with him. My trainer observes he will panic and his mind can shut off.
The more I force him to move forward, or if he gets frazzled, he will walk backwards into anything.
After such an experience - we were returning from a balky trail ride and my riding partner suggested we walk past the driveway. I tried to but Ed began backing up, turning, etc, and I allowed myself to get frazzled, too. So my partner turned into the driveway- in the direction of home. My gelding, still frazzled, then refuses to walk down the driveway to home. If I forced the issue he went backwards the wrong way down the driveway. I didn't have the mind at that moment to walk off property, probably should have tried. It was if he stopped thinking at all, just reacting blindly. So I got off and we did laps up and down past the driveway and onto the road for 200 yards back and forth.
He will go out by himself, which is odd. When we get to a sticking point I use open rein to keep him pointed the right way, and use my voice, and bump him with my legs. I have seen this method work better with him and he remains calmer. He and I have been together for only two months, but my trainer knew him well and we continue to be in a program. I consistently do groundwork and confidence building with him and keep working on leadership/trust.