I too was very frustrated with them last Friday. Instead of making a nice profit, I lost some following their auto-liquidation rules.
I bought three 2025 AMZN put options (long, not short) expiring the same Friday. Initially price went a little bit against me, but later price fell all the way to 2005. When the price reached 2025 again, the puts went ITM, but (to my surprise) were auto-liquidated (at a loss) at that moment.
My available margin was around $45k (again I was long, not short). I later understood this happened because of "projected post expiration margin deficit". Apparently their algo decided I did not have enough $ to own 300 AMZN shares at expiration, however, my intend was never to hold until expiration, but sell before.
Does someone know when this rule gets into effect? Only on the last trading day and if so how late? Or also days before last trading day? And do other brokers have a similar policy?
I would expect a $50k account is sufficient to go long 3 AMZN options, but apparently not