Dell latitude E6420 - plug headphone jack in stop internal speakers to work

 recently bought a Dell latitude E6420 i5-2520M 8GB and I am experiencing a very annoying issue with the speakers.

The sound coming from the speakers worked until I plugged in the headphones jack into the computer for the first time - when I unplugged the headphones internal speakers stop to work completely.

What I have tried so far with no success:

• Uninstall and reinstall windows audio/sound drivers
• Tried Realtek drivers
• Disabled headphones
• Recovery and reinstall Windows 10

What is strange is that every time I uninstall and reinstall the sound drivers the speakers start to work again until i plug the jack of the headphones and again speakers stop to work. Any Idea?

Please let me know what you need to know about my computer to better understand the problem and I will amend the question accordingly.

Thanks!