Keyboard issue : holding ctrl+shift+left/right arrow doesn't work

Hi,

I bought a Dell laptop (Inspiron 17/5000 Series) last month and when I edit text, for example in Microsoft Word, I can press CTRL+SHIFT+LEFT/RIGHT ARROW to select one word. But if I hold the keys, it doesn't continue highlighting text. It is highly annoying, as I would always use that function as part of my job. I checked with an external keyboard, and it worked perfectly fine (it would keep on highlighting more and more text as I held the keys).

Is there any way I can fix my laptop or change settings to make that work? I'll have to return the laptop if I can't fix this.

Thank you.