Keyboard Issues, LEFT SHIFT + LEFT CTRL + L/R ARROW doesn't work on travelmate P645-S windows10

Recently i am facing issues with my laptop. Key combinations doesn't work especially with SHIFT.
List of combinations (Not working) :
LEFT SHIFT + LEFT CTRL + LEFT ARROW
LEFT SHIFT + LEFT CTRL + RIGHT ARROW
LEFT SHIFT + LEFT CTRL + UP ARROW
LEFT SHIFT + LEFT CTRL + DOWN ARROW
RIGHT SHIFT + RIGHT CTRL + RIGHT ARROW

List of combinations (Working) :
RIGHT SHIFT + RIGHT CTRL + RIGHT ARROW
CTRL + C, CTRL + V, CTRL + X
Other than above 'working' combinations no other combination works with CTRL and SHIFT
Please let me know why this issue is occurring!
Is this a hardware issue/ software issue?
i have updated keyboard drivers, also uninstalled and restarted laptop & let drivers install automatically.
Also i have checked if laptop's keyboard is loose or anything... everything is fine on that side.

P.S.
Recently i have upgraded my 4+4 GB RAM to 4+8 GB RAM
this RAM is DDR3 and may not be original :P

Any help is appreciated.

Accepted answers

All comments

yogprabhu

seems like a keyboard hardware issue

JackE

Open ControlPanel. Search 'restore point'. Click 'create a restore point' in the left pane. Click 'system restore' button. Click 'next'. Do you see a restore point listed with a date stamp that approximately coincides with when you first noticed the KB issues? Jack E/NJ

yogprabhu

There is no single previously created checkpoint. Therefore can not restore the system.

JackE

Sorry, you waited too long. These restore points are usually automatically deleted after about a month. To rule in or rule out a keyboard hardware issue, you can try a factory refresh or full reset using the ALT+F10 cold boot method as shown in the video below. If it fails to fix the problem then you should first try to reseat the KB ribbon cable connector at the mainboard to clean the contacts. If the problem persists, then a new keyboard replacement is recommended. Jack E/NJ