I've got message from poloniex:
"As soon as there is a block explorer up to date with the new chain we can attempt to update and sync the wallet, until then it is not possible to be sure we are on the right chain.
Best regards,
Johnny Garcia"
So what about the blockexplorer?
I don't know any Blockexplorer for NAS right now, I'd love to have one, but i have no time to implement it.
There's an, maybe better, alternative to a blockchain explorer: the
public server of tiker 
A public NAS client/wallet, connected and sync to the right chain.