Hall of Lead / Esuna / Quickcast bug?

Dodging all of Odin's mechanics is supposed to be a challenge. I get that. But it seems that in order to throw the player a bone, the system for clearing up a debuff and such should be responsive enough to not work against the player.

For some reason, whenever I get hit by Hall of Lead in Odin, then esuna myself and try to quickcast medica or medicaII quickcast I always start casting rather than getting the instant cast. Yes, quickcast buff is on and takes hold and is on cooldown. No, I am not using a macro. I am pressing the buttons via mouse. The only time I encounter this problem is in Odin after I get hit with Hall of Lead and usually am quickcasting Medica II because Einherjar is coming out.

This has also happened even when I get Hall of Lead, Esuna off the slow, use divine seal then use quickcast and then use medicaII.

I know it could be lag and thought about that, but I have used quickcast plus other spells while fighting Odin and other dungeons with no problems. Also, I have been dodging the mechanics in Odin fairly well and they are pretty unforgiving if you are lagging. This *always* seems to happen after getting hit with Hall of Lead for me.