Move to fixed schedule.

src/sound/footstep.rs

@@ -127,7 +127,7 @@ pub struct FootstepPlugin;
 impl Plugin for FootstepPlugin {
     fn build(&self, app: &mut App) {
         app.add_systems(PreUpdate, added).add_systems(
-            PostUpdate,
+            FixedPostUpdate,
             update.after(TransformSystem::TransformPropagate),
         );
     }