I had the same problem with my GT783R until I realized what the problem was in my case. At one point I swapped out the optical drive for an additional disk drive with a spare optical drive bay caddy. My laptop is the center of my "media lab" and I have a 12-port USB hub plugged into it and lots of part time peripherals that get swapped in and out as the need arises.
I moved a lot of stuff onto a network available storage, consolidated my disk drives, and then swapped the original optical drive back in. I also have a Virtual Clone Drive installed. After all the swapping, the clone drive is F: and the optical drive is G:.
Turns out, after messing with it a bit, that the S-Bar Eject Switch at the top of the laptop is coded to operate against the FIRST "optical" drive it sees. It worked the eject on the Virtual Clone Drive.
After using Disk Management app to swap the drive letters, making my optical drive F:, all is now restored to the expected and preferred behavior.
Hope your situation is as simple to figure out.