I can imagine this has happened for a few different reasons - one is that you have an unfilled order, which the protocol is holding margin for. If that’s true, it seems to be a ‘messaging’ issue, so that you understand why margin is being held. We’re actually looking at some ways to better express this information.
The other possiblity is that you had no order, and that margin was being pulled for no obvious reason, which is definitely a bug.
Hopefully you see this, and you can provide a bit more information so we can narrow down what’s happened!