Does anyone have negative poloniex experience here? What escalation process actually get's them to answer a ticket? Do we have any poloniex reps here?
Don't try use stop limit function when margin trading on Poloniex, it always have error and can make loss your funds, and then you will spend more time for contact support refund you, maybe need one month for wating reply 
I've actually never had this issue - have you ever tried margin trading on the site?
That happens only rarely when a cryptocurrency is very volatile. It would be very hard for the Poloniex platform to keep up with the fast movement of the price resulting in a missed trade. But the good news is this becomes a limit order. If you are patient it will be hit your target price eventually. But do not make the mistake of using selling on the market in your stop orders. You will always not have a good exit price.