Need help with (simple) click to move/ RTS style movement

You can interrupt go.animate using go.cancel_animations.

Alternatively, you can move your game object in the update function using speed , direction, velocity, dt etc

Probably because of z-fighting. If your background’s Z is 0, your sprite (actually your game object) might end up behind it.
Try using 0.1 for the Z value to your mouse_pos to test it.