Druid Mangle Bug when respeccing (NOT dualspec)
Maybe some of this info can help tracking it down.
Last two times i respecced between Feral and Resto it happened.
Before being Resto I was Feral with Mangle (Rank 3) on my char. After unlearning Resto talents and reassigning Feral talents including Mangle my character only had Mangle (Rank 1) for both bear and cat in his spellbook.
On the trainer it shows Mangle (Rank 2)(bear/cat) in green (being able to learn) and Mangle (Rank 3)(bear/cat) in red (unable to learn since i don't know Rank 2). After learning any of the Rank 2 Mangles my character instantly gets all the Mangles including Rank 3.
Seems like after learning any Mangle from the druid trainer my character / the server somehow remembers I used to know Mangle and I don't have to relearn Mangle (Rank 3).
(I also remember respeccing once a few weeks ago and NOT having any issue at all with Mangle (meaning after assigning feral talents i got all the ranks of Mangle without having to learn anything from the trainer); sorry can't remember when exactly, just that it actually worked once :P)