What "check" does the Antimagic shield make?

[PurpleXVI]

It says that it makes a "check" to see if it's disabled or not when it deflects damage, but what is this "check"? What value would I want to increase if I want to keep said check succeeding?

[HousePet]

Its your equilibrium fail chance.

[PurpleXVI]

Its your equilibrium fail chance.

Really? That sounds kind of weird, because even with, like, 1% or 3% fail chance it seems very likely to drop.

[HousePet]

If you get hit more than once per turn, it will check more than once per turn.