What version of Premiere Elements, what computer operating system?
How are you introducing the DVD video files into the project....inserting the DVD disc into the burner tray and then using your Premiere Elements' Add Media/DVD camera or Computer drive/Video Importer or something else?
If you explore the disc while it is in the burner drive tray, how does the file size of VTS_01_1.VOB compare with those of the other files in that series, namely, VTS_01_2.VOB, VTS_01_3.VOB.
If you explore the properties of the dvd video files - are they all DVD compliant? What is the frame size and frame rate of these files?
Let us start here and then decide what next based on the details in your reply.
Also note that some of the VTS_.vob files on your DVD are menu files, not video files. So they won't load into a Premiere Elements project.
You have already specially named only DVD video files with which you are dealing, that is, VTS_01_1.VOB, VTS_01_2.VOB, and VTS_01_03.VOB. These are the DVD video files, and they should import into Premiere Elements.
There is nothing in what you have reported that says that you are working with a menu file from the DVD. It is accepted that the file specifically named VTS_01_0.VOB would be the menu file, and again you have not named it in your problem.
As a related aside, for at least Premiere Elements 13/13.1 and 14 Windows 64 bit, I have observed that the VTS_01_0.VOB (menu file) will be ripped (copied) to the Premiere Elements Add Media..... Video Importer and taken into a project as a Timeline component. But it is of no use to you for the purposes of menus for the project.
Your DVD video files specifically named are my focus for the troubleshooting.