They're not casting Dazzle, they're casting a darkness spell. Try Juggling Lights.
It's their version of Dazzle, and while Juggling Lights will counter it, the game engine still has a tendency to burp at that point (though it's less sensitive than the upon-leaving error). It's safer to just not have Reversal going since the chernovy shouldn't be too difficult to deal with without it unless you're there really early in the game.
I've actually never had the game "burp" at that point, but then I don't enter the screen with Reversal, I cast it after entering.
I mean, sure, it's easier to just cast it at them and take the hits like a champ, but I like to take as little damage as possible and the battle screen makes it easy since a fully charged spell counters any projectile the enemy throws at you.