Following issue

[Ualaa]

My roommate used to play a mage as his main.
And running anywhere, he'd blink as often as possible.

Unfortunately, with 2 or 3 boxing, blink puts you just a bit out of follow range.
Not sure if you have anything like that.

[HPAVC]

Either its lag or there is a buff on the master.

If you follow the slave and don't have problems, I would bet its a lag issue.

That said I used to have this problem a lot before I had decent hardware, it only occurred on mounts (pre-flying) and carrot and a stick on the slaves only was enough to cure it.