Healing Ultima is intense.

[Elurra]

This usually happens if you start healing the moment you stop moving because the game thinks you're still moving. Best to wait about half of a second before you begin casting.

You can also take advantage of this in the opposite way where you can start moving about a half second before a spell finishes casting.

If I really need to cast a heal, I'll usually eat one of the eruptions and then heal myself up after.

That could be it. I do take advantage of the healing on the move trick. Never thought about the opposite causing problems like that, but it makes sense. Thanks for the tips everyone.