You have a pet caught, you just have one last one to defeat...
Suddenly some random mob attacks you, the battle ends.
You don't get to keep what you caught, you don't get the xp for your pets, your pets retain any damage/deaths from the battle, & now you're being attacked by stupid frikkin' mobs.
Why is this able to even happen?
Even if it's a very, very, very low leveled aggressive mob, it can attack you & end the battle.
Please Blizzard, please get rid of the battle interrupts!