Planar Binding Immediately Cancels

[Spikem59]

So I gave Gale the spell Planar Binding, and it literally just does not work. I cast it on Lorroakan's water elemental, which the spell states is a type of creature it can target, and after the log says it failed its saving throw and Gale started concentrating on the spell, it immediately cancelled. He wasn't standing in the AoE of a sleet storm, he didn't take damage, nothing broke his concentration, the spell just flat out cancelled immediately upon casting and wasted a fifth level spell slot. I examined the myrmidons and nothing in their statuses states any sort of immunity to such spells, so what's the deal? Is this just a broken spell?

[Böggen]

I'm experiencing the same thing. It's extremely frustrating and I can't figure out what's causing the spell to fail.