XPS 12 (9Q33, Mid 2013) Laptop Screen Issue

Question

The issue started occurring just few weeks before the end of warranty. My laptop stopped detecting the the internal screen in Windows. When booted to Windows with no other screen connected, the internal screen is blank. If the external screen is connected during booting, internal screen is enabled but with settings like resolution taken from the external screen causing everything to be shifted to left and the external screen is blank. In fact it seems that Windows thinks the external screen is internal as touches on internal screen are still working. BIOS, Windows recovery, Windows booting are correctly displayed on the internal screen - the problem is with Windows logon screen and further. Also when connected to the external screen, Windows doesn't show internal screen in the dropdown in the Screen Resolution menu.  When using Ubuntu, the OS correctly recognises and works with internal or both screens. I tried reinstalling vanilla windows, next used Dell Recovery to reset to the initial state and nothing helped - this is why I think this isn't Windows issue but hardware issue that affects Windows. I followed some advices from the Dell support portal and tried to install the firmware update (XK8DT) but got "AuxUpdate MFC Application has stopped working" error and couldn't proceed. Installed all drivers including the BIOS update from the Dell website - nothing helped. Run the diagnostics from F12 menu - they all passed reporting no problems. Restored BIOS defaults - no difference. Run Online Helpdesk tests, no problems detected.
The biggest problem is that I thought the problem is with Windows initially and waited to reinstall it due to being busy at work and not having time to back up all my files and was very disappointed to realise it is not a software issue 3 weeks after my warranty ended.
Here are two videos I recorded to demonstrate the problem:
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Answer 1

Since I haven't got any response I will recap the issue:
When I boot the laptop with external screen disconnected:
i can see the BIOS and the Windows loading screen on the internal screen (and Windows recovery etc).
when Windows is loaded i can't see the logon screen or home screen but a blank screen only.
when i connect external screen after Windows is loaded, i don't see anything on the internal and external screen.
When I boot the laptop with external screen connected:
when I boot and the lid is closed, Windows works perfectly fine on the external screen. When I open the lid, the internal screen is still blank, touch works though.
when i boot and the lid is open, Windows is displayed on the internal screen and the external screen is blank. The displayed home screen is broken on the internal screen since it uses the settings like resolution from the external screen, since the external screen's resolution is higher. 
In both boot scenarios, when the external screen is connected, the Windows screen properties dialog doesn't show the internal screen, only external.
I reinstalled windows from the recovery partition but it didn't solve the problem.
I run diagnostics from the Dell Support website it all passed.
I updated all drivers including BIOS it didn't help.
I run BIOS diagnostics, they all pass as on this video: 
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I don't know what to do, this happened when warranty was still valid, i followed different suggestions from the support page and thought it is a software issue. Didn't reinstall Windows as i had couple of projects behind the schedule and didn't have time to back everything up correctly. After i did reinstall and found that this isn't a software issue, the warranty was already expired by two weeks.