Yobit seems to have unethical practice of blocking wallets from exchanging high yield currencies. Not only was i scammed of transaction fees which was higher than what was stated (double) and they refuse to reply me, also they block all incoming deposit of currency having higher than market exchange rates i observed everytime.
When NEM was double rate of market, it blocked all currency from going in , i suspect its possible they will use it to gain for themselves first and released it when the double rate buyers were cleared.