Try a different approach on resolving the issue

src/fos/core/FOSMod.java

@@ -22,7 +22,6 @@
 import fos.ui.*;
 import fos.ui.menus.*;
 import mindustry.ai.Pathfinder;
-import mindustry.core.GameState;
 import mindustry.game.*;
 import mindustry.gen.*;
 import mindustry.mod.Mod;
@@ -154,14 +153,11 @@ public void init() {
         Reflect.<Seq<Prov<Pathfinder.Flowfield>>>get(pathfinder, "fieldTypes").add(() -> pt);
         Events.on(EventType.WorldLoadEvent.class, e -> {
             if (!net.client()) {
+                FOSVars.fposVector.setZero();
                 // FIXME: sometimes breaks for unknown reason
                 Reflect.invoke(pathfinder, "preloadPath", new Object[]{pt}, Pathfinder.Flowfield.class);
             }
         });
-        Events.on(EventType.StateChangeEvent.class, e -> {
-            // reset the flowfield's vector on exit.
-            if (e.to == GameState.State.menu) FOSVars.fposVector.setZero();
-        });
 
         //anything after this should not be initialized on dedicated servers.
         if (headless) return;