However, beyond that there is a suggestion that there may be issues with the raw compression for different DNG sources.
Where is this suggested? I know ACR compresses raw otherwise (= better) than dcraw and cr2hdr that uses it, but apart from that converting a cr2 to raw dng shouldn't touch the raw data, but simply put it into another container, or am I mistaken? They might do something to the wb settings though, and I remember that some Maker Notes are said to be lost on conversion(?).
Probably setting an older dng version and re-compress the dng could fix part of the problem, and anyhow I very much doubt DxO isn't able to read the open sped'ed dng, much more likely they simply boycott Adobe wherever they can.