Buggy multiseat mounts

I have found that if I use any kind of multiseat mount, (2, 3 or 5) that if my slaves use interact with target on me the one who mounts first it fails and bugs out.

If I use mouse broadcasting and right click on all that seems to work fine.

Is this a change from Blizzards end? I use ISboxer so not sure if that has anything to do with it.. all other IWT works fine, so I doubt it.

I've always done the mouse broadcast way using interact with object (if I'm saying that correctly) which I also use for herbing/mining.
I think I remember the interact with target bugging out a long time ago and that's why I used this method.

It used to be flawless for me. I wondered if it was a nerf because of pvp using mounts to get around.