You can try moving her shoulder over when you get that and moving her hq over. It gets her shoulders out of the way so that there is room for the hq to make the change. You said counter cantering, but I'm thinking you mean cross firing. Is that right?
I'll occasionally get the cross fire, online that is all Sass ever did. It wasn't until I moved her shoulders way out of the way that she was able to get the change on her back end. She could be a bit impulsive there in which case doing circles on the same lead until she is relaxed and pushing off the hq could help. I'll watch the last part again and see if she looked impulsive. Oh and also try a small jump or ground pole, that gives them enough air time usually to get it. Just make a pattern of that and get to the ground pole, then do it next to the ground pole so that the thought is in her head to get that air.
PS I'm sorry if your horse is a gelding, I wasn't really paying attention to that until I started writing this! : )