Here's how I copy my personal video DVDs:
1 - mount the DVD master disk on the Desktop.
2 - copy the AUDIO_TS and VIDEO_TS folders to a folder on the Desktop.
3 - name the folder to what you want the disk to show once burned and mounted on a computer.
4- launch Disk Utility and select the File ➙ New Image ➙ New Image from Folder option.

5 - select the folder to burn on the Desktop.
6 - select Encryption: none and Image Format: read-only

5 - click Save.
6 - mount the disk image and launch DVD Player (you'll need to use the File ➙ Open DVD Media and select the VIDEO_TS folder to play) to make sure the copy is good and plays as it should.
7 - put a blank DVD disc in the optical drive.
8 - Control (right) - click on the disk image and select "Burn Disk Image XXXX to disc…" from the contextual menu:

9 - in the Burn window select the slowest speed available (2x-4x if possible) to assure the best burn quality. Always use top quality media: Verbatim, Maxell or Taiyo Yuden DVD-R are the most recommended in these forums.

It's good practice to "rest" the optical drive between 3-4 burns to let the unit's lasers to cool down.
Give it a try and let me know how it went.