Uhhhh, aren't the DNG files from your Leica ALREADY DNGs? I don't understand how converting a DNG into a dng could possibly result in a file size reduction. I'd just use the 'move' option in the LR import dialog to bring the files from the camera into the LR file folder system.
Known fact: see
here in Leica Forum and
here in an uncharacteristically sensible discussion at DPR
The DNG Convertor, stand-alone or in LR's "Copy as DNG" (in LR v.1 through v.5.7) applies lossless compression to the camera's DNG's. I know it's happened when I see the file ext change from .DNG to .dng, as I've set that in my LR Prefs. I know know it's not happening now because, like I said, 'what is coming into LR is the full-size .DNG files, and at the end of the import routine I get the "Non-raw files were not converted to DNG" notice'.
Maybe I need to report this to Adobe. Just that someone here usually knows the answers on these sort of things, and some are on speaking terms with the ACR team... I'd post on the Leica forum but it would only arouse the anti-Adobe mob, re-start a fight over Copy vs Copy as DNG, and give space to those whose hobby it is to trash LR with "this upgrade is the worst ever" stuff they probably have saved on their drives ready (and have had to hold back on a
long time in the long wait for LR6
)
Jim
PS: Library>Convert Photo to DNG does work, it's just the Copy as DNG at Import that's not working in LR6