Yes Andrew I am aware and agree there are benefits for the use of dng but there are also cons, which I have to be aware of, since I use software that does not work with dng files.
I can see how the OP got caught with his xmp data getting "corrupted" because he was not fully informed on the use of dng files.
Often on the forums advice is given "convert to dng" without a word of caution to the user to become informed before proceeding, as if it is some magical file format