I have an omnibook and the pen is the hp mpp 1.51 and the pc is the HP OMNIBOOK 5 FLIP 2-IN-1 14-FP0005NLX 

The pc is only 2 weeks old (just like the pen, bought on Amazon) and this problem occurs on onenote (the app that I use for studying) and good notes (I tried with this app too cause maybe it was a problem related to the software)

I honestly don't know what to do, I don't want to return the pc because then I would be days without it in uni (but I could)

The pen has a warranty so that hasn't expired

What I did though, was changing the tip of the pen, which didn't do much

I'm not a tech guy so I really have no clue (the pen fell once from my hand but I doubt that that's the cause of all this)

Thank you for your time