I believe the raptors have fairly large FW tanks. I have read numerous posts on various forums regarding the issue you describe. Keystone uses flexible strapping material under the tanks that allows for expansion or sort of cradles the tanks. I have heard of these straps breaking or coming loose where they secure to the frame due to inadequate anchoring at the factory. Check out
http://www.rv.net/forum/index.cfm and do a search there. Also try a search on this forum. You should find solutions there. If you are handy and have the ambition, you can fix it yourself. It will cost $$$ if you have a dealer do it. You won't likely get Keystone to step up to the plate as you warrranty is well over.
As long as your tank hasn't cracked, you should be able to make and install adequate tank supports.