Spells Constantly Being Interrupted (Specifically Necro)

[Axoc]

I don't understand the mechanic of "Your spell is interrupted."

I understand that fizzling is basically random and based on invisible skill checks, but I'm talking about the actual interruption. It seems to 100% interrupt if you move while casting, but not if you turn the way your character is facing. Sometimes I'll just be standing there and get 3 back-to-back interrupts without moving or turning my character's direction. Is there a skill I need to train that governs interrupts or is there always a chance that my spells will randomly interrupt? I've noticed that this happens when I take damage more often than when I'm not taking damage, but about five minutes ago I had another one of those back-to-back triple interrupts. In that instance, I didn't take a single point of damage until after my third interrupt.

It's infuriating, and it's often the difference between me having to FD, lose my pet, and go med all the way back to full versus me easily killing the mob.

Edit: It seems like swimming also has a 100% interrupt rate. Do which zone you're in and which spell you're casting contribute to your interrupt rate?