Hi @sylviavila ,
Here’s a link to the [https://download.lenovo.com/pccbbs/mobiles_pdf/tp-e480-e485-r480-hmm-en.pdf|service manual] for your laptop. Scroll to p.84 to view the necessary pre-requisite steps and then the procedure to remove the LCD panel.
I don’t know your laptop but it may be that the LVDS cable is an integral part of the LCD panel and is permanently connected to it and only plugs into the systemboard connector.
It could be that you have an intermittent connection in the LCD panel itself.
A couple of things to try first.
On p.27 of the manual it details how to access the UEFI diagnostic program. In the program there is a LCD test which may help to give a further idea as to the problem.
Connect an external monitor to the laptop’s HDMI port and check if its’ display is OK or doing the same as the laptop’s display, just to help narrow the problem down. If it is OK then more than likely it is a LVDS cable connection or LCD panel problem. (Note: a TV, if it has HDMI port, can be used as an external monitor.)