I strongly suspect that it was the firms hedge position which killed them. They probably realised a long time ago that clients were simply picking off the low hanging fruit it terms of trading in line with 'the peg'. So in order to mitigate losses the firm has to hedge in line with the client base. This is all fine and dandy until the peg was removed. I suspect at that point the firm (along with several other firms by the looks) simply ended up providing liquidity (fixed spread sizes etc) in their own market which was simply not there in the underlying (which was where the firms hedge was placed.)
So maybe they ended up being stuck with their hedge position whilst some clients were able to exit their positions due to the automation of the platform (and the fact that the maximum spread is fixed)?
not all of these firms are fully hedged, I'm not sure whether they would let clients get out of any positions when there is no liquidity for themselves (the platform might be automated but it would be silly for it to blindly allow orders to be executed in a situation like this and they don't appear to have done so given some of the complaints - they will have a clause regarding any fixed spreads in a situation like this) - I would assume there are quite a few clients who's stopped were slipped massively and who have sustained losses larger than the amount of funds they had deposited, at least that seems to be the indication - people getting fills far away from where their stop was - given the leverage they were offering it is quite possible that they could have a situation where a bunch of clients have taken very large losses that can't be covered. Hopefully the clients with positive balances will get fully compensated one way or another.