Laptops Laptop screen weird behaviour

[zoozoo]

The screen of my laptop in behaving weirdly since last 7-8 months. The display on the screen starts moving up & down every 2-3 seconds and is not stable at all. This becomes very irritating & strain to the eyes. I have attached a picture of the screen. I think you are able to make out looking at the picture. I also recorded a 5 sec video but unable to upload here. Is there any way I can share the video? However, connecting an external display via HDMI resolves the issue & I have to use my laptop always connected to an external display. My laptop has become immobile & as good as a workstation.
1. Can you please suggest where the problem lies?
2. What component needs replacement or repair?
I can open the back lid of the laptop and check as per your suggestions. Specifications of the laptop is as below

Make & Model: DELL Inspiron 15-7579 touch screen
Year: 2017
Specs: 8 GB RAM / Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz[Cores 2] [Logical processors 4]
Operating System: Microsoft Windows 10 Home

 

[bigb123]

Your display cable or a display component on motherboard is dying...you will have to take it to a service center or a third party repair shop to replace the faulty component.

 

[zoozoo]

Your display cable or a display component on motherboard is dying...you will have to take it to a service center or a third party repair shop to replace the faulty component.

A faulty display component should also impact the output thru the external monitor. No? Connecting with an external monitor works absolutely fine.

 

[Heisen]

When external display is connected, is the laptop screen is also in use? Or you just use the external display only?

Use both displays at the same time see what happens.

 

[john1911]

However, connecting an external display via HDMI resolves the issue

I'm not sure I understood it clearly.

Do you mean to say that the external display (via HDMI) is working without any issues?
Or do you mean that the laptop's display stops flickering when an external display is connected to the HDMI port on the laptop?

 

[zoozoo]

When external display is connected, is the laptop screen is also in use? Or you just use the external display only?

Use both displays at the same time see what happens.

Either way. I used with both screens displaying content at the same time and I have used with laptop display turned off. In the first case the laptop screen keeps on flickering while the external monitor screen display is steady.
In the second case the laptop display is switched off and the external display screen is steady.

I'm not sure I understood it clearly.

Do you mean to say that the external display (via HDMI) is working without any issues?
Or do you mean that the laptop's display stops flickering when an external display is connected to the HDMI port on the laptop?

Yes the external display via HDMI works without any issue. The external display is steady like it should be. The laptop’s screen continues to flicker even if the laptop is connected to the external display. The external display screen is rock solid.