Th cd are getting stuck in my gpx kccd6316dt, I

I have observed this happen in two different scenarios:

1) I have observed this happen when the unit is not level. If the unit is tilted up in the front (down in the back) the CD can slide off the back of the tray when the tray moves outward while the CD is still spinning. To avoid this do not press the OPEN/CLOSE button while the CD is playing - press STOP first and give it a few seconds to stop before pressing OPEN/CLOSE. Make sure the unit is level.

2) I have also observed this with CD's that have any kind of stickiness around the label side of the hub area. This may be from debris or adhesive from self-stick labels. Any stickiness delays the CD from dropping down on the tray before the tray starts moving outward causing the CD to drop behind the tray. Clean any CDs that have any stickiness on the label side of the hub area.

If some sticky CDs have been played, some of that stickiness may have transferred to the label side of the internal mechanism that "sandwiches" the CD. If so, that part of the mechanism may need gentle cleaning with alcohol and a lint-free cloth or swab. It is necessary to remove the top cover to very carefully clean that part of the "CD sandwich" mechanism.

Both of these two scenarios may be present, so you may have to deal with both cases.

Is it still under warrenty?

Either it is worn out or it has a manufacturing defect.