I normally have x2x running to control my media PC.  It claims the cursor and keyboard if I move the mouse off the right side of the screen.

Prior to Minecraft 1.14 (f.e. 1.13.2), Minecraft's capture of the mouse completely prevented this from happening (as desired).

Since 1.14, if x2x is running, when I turn to the right in the game (i.e. move my mouse to the right more than a small amount), Minecraft does not lose its capture of the mouse, but the game almost always glitches soon after.

Typically some amount of recent movement is reset (I suddenly move to a previous position) and my orientation will also change (often drastically).