>>398924176
Make a new animation that resets all the shapekeys to 0, except your visemes, and except any blink/lowerlid shapekeys that you use with VRC's eye tracking.
Edit your FX controller and right below the base layer, make a new layer (set its weight to 1). have this reset animation playing always, all the time on this layer. then turn OFF write defaults in all of your states in every layer of your FX controller.