Didn't dump the waste tanks.......
Did you take it to them with stuff in waste tanks?
Does that CW have dump station on site?
Did you tell them tanks have stuff in them?
Other than a few gallons of water left behind from rinsing/flushing when you dumped them there shouldn't be anything in them when you took it in for winterizing.
When winterizing anti-freeze should have been run thru faucets and flowed into 'P' traps will some going into grey
Anti-freeze poured down toilet into black tank and then some in bowl.
Unless tanks were FULL should be room for expansion so hopefully no cracks.