After your comment I looked into 2.
I also have slippage when in combat and its annoying because I can't turn my character or move my character without the mouse cursor slipping or just staying put.
Moods Each user can define text to display with normal chat messages to indicate the speaker's mood when speaking.
Deeper dive: DCS FAQ on Steam.
Deeper dive: I referenced piece while picking out my HOTAS.
Just press the up or down arrow key while the typing cursor is in the chat entry box to access chat history entries.
So the "quirk" is quite possibly a feature.
But first, install the right driver.