Hrm. That's awkward, because it means our older records might be affected but it wouldn't become apparent until they 'caught up'. I'll try it and find out. Do you expect the fix to correct the problem in existing saves, or only prevent it from happening to new saves?
How does it happen, if you don't mind me asking? I presume forceAction is how you trigger the vengeance status, but I would expect bugs in it to break the battle in which it occurs...not silently corrupt something that breaks the next battle Malayna's in. Is something about the vengeance trigger's state preserved between battles? If so, maybe you can retroactively fix it with a check at battle start.