What were you using to plan and fly the mapping mission?
Before RTH drones were available, you could produce reasonably accurate maps with the Phantom 4 pro, but easier than with a Mavic 3 pro because you could use apps like DroneDeploy to plan...
It's not so much that you can edit the dng files.
It's that you must edit the dng files unless you want them to look dull and flat.
Dng files aren't meant to be left unedited and it sounds like you've done nothing to this one except open it in...
The drone didn't lose signal and drop, it lost power and dropped.
When there is a sudden power loss, two things happen.
1. The drone drops
2. You are left looking at a controller that says Connection Lost.
Either the battery wasn't locked in...
Mavic 3 pro lifeless and flat ?
Not in my experience.
Perhaps if you could upload a couple of examples to Dropbox, Google Drive or similar and post a link, some of the photographers might be able to give you some suggestions to improve your images?