Cuerzor

Ok I resolved that by uninstalling and reinstalling an older touchpad driver, and this no longer happens.
So it can be a touchpad compatibility problem.

Well I made a test and found something weird.
After you closed a GUI, like inventory or chests, and return to the game playing, the actual position of cursor will not move for seconds. But after that your cursor will start moving and get out of window again.
I uploaded a video for resolving this issue.

I found that if you move your mouse slowly, this will not happen. But if you move it very fast it will always get out of the window, and after that even you move slowly again, your mouse will never be locked into the window until you open inventory or menu.
Is this useful?

Yes my PC is a laptop and its screen can be touched to play.
Maybe all players met this issue are the same as me?

Tried to disable "Allow Edge Swipe", nothing changed, the mouse still runs away from the game...
😞

I met this on 1.14.0 too. And I found that it doesn't happen at start, after seconds of time it will happen.
My OS is Windows 10 1803.