Spamming Spells While Moving Causes Endurance to Regen

By holding down a spell while moving (to cause constant spellcast interruptions) your endurance will actually regenerate.

It appears that when you spam a spell and it is interrupted by movement it confuses the game into thinking you are standing still causing your endurance to regenerate as if you were not moving. Also, if done while sprinting it does not always consume the endurance to sprint since the game appears to think you aren't moving.