hitting the "CLOSE" button on a composite portfolio should bring the composite portfolio account to 0 positions but more importantly, every account to 0 positions. So it can be safe.
I ran into a situation where a slave account was at -2, the portfolio at 2 and when I hit "CLOSE", the slave account became -4 and the portfolio account 0.
Instead of trusting the portfolio account positions to close the others, each slave account positions should be checked to make sure they are all closed to exactly 0 positions. And then the portfolio account position can be reset to 0.
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