Things to try and narrow down the issues and hopefully to resolve them.
a). Have you got the latest WLAN drivers installed in the laptop?
b). Download, install and run a WiFi discovery program to check the signal strength of the WiFi networks as detected by the laptop’s WLAN adapter.
Here’s a link that shows what the signal levels in dBm mean as far as a ”good” signal level is concerned. Scroll down to the Ideal Signal Strength section.
If the signal strength in the laptop is a lot different to what is shown in the desktop, (load the same program in it), given that the laptop is in the same location, there may be a problem with the WiFi antenna connections in the laptop.
Here’s the hardware maintenance manual for the laptop.
Go to p.39 to view the necessary pre-requisite steps and then the procedure to remove the WLAN card. This will allow you to check whether the antenna cables are securely connected to the card.
c). Start the laptop in safe mode with networking and check if the WiFi remains stable etc. it may be a program that is causing the problem e.g. AV (anti virus) or other 3rd party programs that are running in the background.
With safe mode only Windows and Windows drivers are loaded so it just a basic computer and OS but at least it may help to indicate a problem or not. If no problems in safe mode then it is either a driver problem or a 3rd party program problem. If there are also problems when in safe mode then it may be a hardware problem e.g. faulty WLAN card perhaps
Check in Task Manager > Start-up to see what programs are being loaded on Start-up and whether they’re necessary or not. Some maybe are necessary, so if you don’t know what they’re for etc, Google the name to find out. You can always disable them by right clicking on their entry in Start up and selecting disable, then restart the laptop and check if it improves it or not. To re-enable them simply go back into Task manager > Startup, right click on the program and select enable
Create a Win 10 battery report to check on the status of the battery. Check design capacity versus full charge capacity
a). Have you got the latest video drivers installed?
b). Try moving the screen back a bit or forward a bit and check if the flickering can be made to happen by doing this. If so it may be a loose video cable connection (at either end, motherboard or panel) or perhaps a damaged video cable where it passes through the hinge to get to the lid from the motherboard case. The hardware manual will show how to access the systemboard and the LCD panel
There is no order of priority in the suggestions merely things to check.
Hopefully a start.