> Market halts are completely different from what we are discussing

I'm not talking about market halts. I'm saying when all the buy-orders vanish from the marketplace, it results in a "flash crash". Hitting the "sell" button will do really weird things at these times.

After all, a "sell" can only mechanically happen if the market pairs you up with a "buy". That's just how the stock market works. If there's no buyers, you can't sell, even if you're hitting the "sell" button.