I had a look at the files and there is nothing wrong with the DNG file, structurally (on the other hand, there is quite a bit wrong with the JPG, seems Samsung (Android?) is still writing malformed JPG file, nothing bad or preventing you to work with them, but still).
The problem is that there isn't an embedded preview in it, at least not one at the expected place (there is one, but it's not at the “normal” place, besides it's thumbnail sized, only 496x280 pixels so quite useless).
So for your Samsung, I suggest you either shoot RAW+JPG or you edit them in e.g. Camera Raw or Lightroom and have it update the DNG (and preview).
Interestingly, I saved again as DNG in camera raw and the file size went down from 18MB to just over 9 MB, from analysing the differences, this seems to be due to the (lossless) compression of the raw data as used by Adobe.
Hope this helps,
Hayo