It's a known problems with the Sia wallet. Once it has too many transaction inputs in the wallet database it chokes and can't send large transactions anymore. The Devs are currently working on solving this and it should be fixed in the next release (1.1.0).
Someone from shapeshift also just joined the slack to ask what's up with the wallet. They're a lot more responsive than the poloniex staff 😀
I put up a directory as a host a while ago, but it pretty much deducted the entire amount of an incomining original transaction - how do I get that amount back? It's not showing in my wallet and it's been more than 12 weeks. Is it lost because that pc with the host went down? Why was it that amount, I thought it would be much much less...not some arbitrary incoming transaction amnount!