Fidor is just upgrading their API for our interface with them and there's no risk to anyone's money.
It would be great if you could post some evidence of this in form of a document/mail whatever you received from Fidor.
Meanwhile I suggest that you credit customers accounts manually. That takes some time but not too long; after all kraken is still small. But to get huge you need customers faith. And to win that (or not to lose it) nothing is more important than to transfer their money on time.