Elastic Search is known to drop your data in some occasions. I think it's fair to advise against using it as your source of truth (or anything built on top of it like Crate).
With the amount of attention and support this has received from both Crate and ES, coupled with the amount of progress that's been made against these issues, I don't think it's a fair to advise against using either as a source of truth.
That said, they are checksumming a hell of a lot more than before, so there's a chance.