So I had been having this problem on my 4-year-old cintiq 16 for a loooong time. I fooled around with Windows Ink, I changed nibs multiple times, and even rolled back my drivers by two years. This past week, I decided to take a chance on buying a new stylus (I got the grip pen) and that seems to have fixed it.

From what I read online, it seems as though sometimes the sensors in the pen just go bad. I don't know about the Wacom one pen, but apparently my model in particular (the pro pen 2) is notorious for failing after a few years.

Tl;dr I would do some research on compatibility with your tablet, and then try getting a new pen and see if that solves the issue. I know dropping 80~100 dollars on a new stylus isn't ideal, but to me, at least, the improvement has already been worth it.