Okay so - Wren's storyline involves a lot of anger issues that run in their family and were the reason for their father's downfall and them kind of over-correcting into the other direction to deal.

So I was thinking - it's more than just when they get angry, but when they get angry and bottle it up rather than deal with it (a bad habit of theirs) something bad happens when it boils over. Literally blank out and just get violent. And at first it takes a bit of bottling up before that happens, but with every subsequent explosion it takes less and less before the next one?