Please help me – Buddy Sour Question

I need an answer to a specific question regarding buddy sour. My gelding has never been sour before. This just started – is there a reason why this would all the sudden be an issue? I have 2 horses and they are both buddy sour on each other. Both act up. But I am the only rider so I can’t work them at the same time. I plan to try the technique of workng them when they are together and letting them rest away. Can I do this by myself? I was wondering if I tied one horse, and worked the other I’m riding around the tied horse. Then walk away and as long as he behaves, he can rest. If he acts up again, I go back to the buddy that is tied and work more. Will that work??? And how long does this take? Should I expect it work after a few days of doing this or is it always on ongoing issue?
(Since both are sour, I’ll have to ride each one seperatly and tie the one I’m not riding)
ONe last specific question: My gelding is buddy sour but if I take him away from the property in a trailer, and he is around other horses, he is fine. He does not seem to remember his partner that we left home.Is that normal? Please help bkmeier@suddenlink.net