Encountered same notice / restriction from TDA for a couple weeks now.
The brokers I talked to said that the notice is NOT due to anything wrong with the company rather I was told by two different brokers when I placed orders that the restriction has been put in place so they can more closely monitor trading activity.
One broker used the term "possible liquidity issues for some trader accounts" could be a reason for the closer monitoring. I think I know what that means if you read between the lines, but I don't know for sure so you'll have to assign your own meaning.
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