It happens when I'm fighting the superbosses such as
Spoiler
That big monster in the swamp and Professor Nebilim
It seems to happen most frequently with the "Dying Moon" mystic arte. A mystic arte (or Hi-ougi in the Japanese version) is a character's Super Saiyan ultra-beatdown attack which works reeeallly well on bosses.
I can't tell you how annoying it is, having spent more than a half hour beating down the bad guy, to launch dying moon, have Anise hit about 15 times, make the big super hit, then do the launch into the air and hit 15 more times ...
... and the game freezes. Right there. Never moves again. I have to fight the boss over AGAIN.
It seems to only happen on the attacks on the second playthrough or later.
Another annoying thing is when the "rhythm" skill interferes with the launching of a mystic arte, since both are keyed to the x button. So instead of either casting or blasting, the character just stands there locked in the charge animation, like a statue , for close to a full minute of game time. Meanwhile, the superboss is killing all my characters.
This seems to be avoidable by turning off the "rhythm" skill, making it useless.
All of which is NOT to say that it's a bad game. Storywise, it's close to my favorite. The game mechanics and things to do and the Albiore and the SF aspect all combine to make it a really, really cool experience. So good I played it straight through again after playing it the first time. But , alas, it's still just a smidge flawed.
Respectfully,
Brian P.