I can help you solve that riddle.
I've been making textures for DCS for a while and randomly some **_db.lua or some description.lua just wouldn't work, exaclty like it happens to you.
The culprit is the text editing software you use.
Whenever I used Notepad to open any DCS text files it always made a mess...
If you use Wordpad you're golden.
Trust me, it works!
As a test, try to add another vehicle as Suntsag said, using Wordpad it'll work.