>>293639037
If you have eye tracking, VRChat uses the first 4 shapekeys to control blinking. If any of these shapekeys are actually mouth shapekeys and not "left blink, right blink, left lowerlid, right lowerlid", you'll notice your mouth moving instead.
You'll have to re-export from blender with your shapekeys re-ordered, either with blanks for the first 4 or with proper blink shapekeys.