Chelonian Gate is a channeled GCD, like Anatman. If you take damage equal to 30% of your max HP, it grants you a buff (Auspicious Trance) that allows you to cast Divine Cataract, another GCD, doing a fat 1000 potency.
It seems like with this option enabled, the frame that a GCD rolls you queue an auto-attack, which will intermittently cancel the channel and prevent you from casting it.
I don't seem to hit this issue if I don't swiftcast Chelonian Gate.
Incredibly specific BLU issue:
Chelonian Gate is a channeled GCD, like Anatman. If you take damage equal to 30% of your max HP, it grants you a buff (Auspicious Trance) that allows you to cast Divine Cataract, another GCD, doing a fat 1000 potency.
It seems like with this option enabled, the frame that a GCD rolls you queue an auto-attack, which will intermittently cancel the channel and prevent you from casting it.
I don't seem to hit this issue if I don't swiftcast Chelonian Gate.
Video example:
https://www.youtube.com/watch?v=QGznAYe0_x8
Frame GCD rolls:
Note: The ability to automatically disable Enable Auto Attacks on Spell for BLU would, imo, be just as good of a solution.