Originally Posted by apachewhitesox
What I do is when he backs up I think well fine you want to back up you can back up.
sadly this will probably cause the problem to worsen, as it quickly and simply teaches the horse that "mounting = backup". It could also be why the problem has persisted. Also, because he's already backing and you ask for more/continued backing, he might take this as though you want him to back faster, possibly leading trotting backwards (although unlikely)
This is why linda parelli's philosiphy of "you wanna do that? We're going to do that! But we're only going to stop when I say!" is great at amplifying problems.