Bittrex seems to be using your coins to manipulate pricing. This is what happens:
The price of the coin you have, has been stable or gradually pushed down over an extended period of time.You have a substantial position in a coin stored on the Bittrex exchange. You decide to transfer the coins to a wallet. When done, suddenly the price explodes upwards.
This pattern sounds familiar and the same thing could be happening with Maidsafe. There are many reasons why this could happen, but this one you can avoid yourself. This doesn’t only happen at Bittrex, Poloniex seemingly does it as well. Of course the same thing counts for Hitbtc.
So avoid keeping your Maidsafe on exchanges.