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I feel your pain. We just bought a new house and because the old loan was paid off, we took a 21-point hit. (Not as bad as yours, but STILL...) If we'd taken out a car loan and a 2,500,000 new mortgage, we'd have only lost ten points. IDIOTIC.
What we all need to do is run up a bunch of medical debt and not pay any of it.
That's wierd: to be clear, you have other non-AU credit cards which have balances on them?
There likely wasn't any deliquency or worse on your reports if you had a 787, either something changed (and that seems extreme for even all your credit cards reporting zero) or it could be a bug which occasionally I've heard of over time where there will be a big swing on the next update it's back to normal. It's never happened to me so I have no idea what causes this.
Before declaring the sky is falling, I'd wait for the next update just in case it's a glitch, and if it's still down near 700, I'd pull a report personally if you haven't done so already and go over it incredibly carefully as I'm fully in agreement with your WTH exclamation from what's stated.