diff --git a/Source/Client/Patches/GravshipTravelSessionPatches.cs b/Source/Client/Patches/GravshipTravelSessionPatches.cs
index 4939f821c..5543893c1 100644
--- a/Source/Client/Patches/GravshipTravelSessionPatches.cs
+++ b/Source/Client/Patches/GravshipTravelSessionPatches.cs
@@ -38,7 +38,13 @@ static void Postfix(Dialog_MessageBox __instance)
             if (Multiplayer.Client == null) return;
             if (!Multiplayer.ExecutingCmds) return;
 
-            GravshipTravelUtils.CloseSessionAt(Find.CurrentMap.Tile);
+            // Cancelling is a synced command, so this runs on every peer. Using Find.CurrentMap here is
+            // non-deterministic: it's the map each peer's camera happens to be on, not synchronized state.
+            // A peer whose camera is on another map would call CloseSessionAt with the wrong tile and never
+            // close the gravship session, leaving that map paused only for them -> the per-map tick counts
+            // diverge and the game desyncs. There is exactly one open GravshipTravelSession at prelaunch time,
+            // so close it by looking it up rather than by the local camera.
+            GravshipTravelUtils.CloseAllSessions();
             GravshipTravelUtils.CloseGravshipPrelaunchDialog();
         }
     }
diff --git a/Source/Client/Persistent/GravshipTravelSession.cs b/Source/Client/Persistent/GravshipTravelSession.cs
index 92461b7b8..8e8de83e4 100644
--- a/Source/Client/Persistent/GravshipTravelSession.cs
+++ b/Source/Client/Persistent/GravshipTravelSession.cs
@@ -57,6 +57,22 @@ public static void CloseSessionAt(PlanetTile tile)
         }
     }
 
+    // Closes every open GravshipTravelSession, independent of the local camera (Find.CurrentMap).
+    // Used by the prelaunch-cancel path, which runs as a synced command on all peers: closing by the
+    // local camera's tile is non-deterministic and leaves the session (and thus the map's pause) alive
+    // on peers looking at another map. There is only ever one such session while a launch is pending.
+    public static void CloseAllSessions()
+    {
+        foreach (var sessionManager in Multiplayer.game.mapComps.Select(mp => mp.sessionManager))
+        {
+            foreach (var session in sessionManager.AllSessions.OfType<GravshipTravelSession>().ToList())
+            {
+                session.Map.MpComp()?.sessionManager?.RemoveSession(session);
+                session.StopPausing();
+            }
+        }
+    }
+
     public static bool TryGetSessionAt(PlanetTile takeoffTile, out GravshipTravelSession session)
     {
         session = null;