Cannot beat Dragons (The Formless, Fangscorcher) once they sit on the ledge

Someone else reported that this glitch will happen if you are using a "trainer" to keep your manna at max and also cooldowns at instant, etc... He suggested if you are using a trainer for those 2 things to toggle them off for a few seconds and that it would fix the problem. That is if that was your problem to begin with.  Sorry, just passing on info, not judging.