When using Line or Curve tool with a large brush, and grid snap turned on, the line moves by itself, often preventing you from drawing the line where you intend.
Before completing the line, if you move your cursor to the same X or Y coordinate of the first click, the line moves away from the cursor.
It only starts happening once your brush is large enough. The larger the brush, the worse the issue becomes.
Line and Curve tool both affected.