So you lose both video and audio when the headphones are plugged in - correct?
Make and model headphones? Which model Samsung? Do you have the User Guide/Manual for the TV?
Having the onboard speakers disabled would be expected when headphones are in use but not video.
Have you tried your headphones on another TV or tried other headphones on Samsung Smart TV.
Determine if the problem follows the headset or stays with the TV.
If the problem stays with the TV, I would suspect some sort of short circuit within the TV's headphone jack.