diff --git a/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/HumanAIController.cs b/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/HumanAIController.cs
index 4479bdb81..e1eb0c40e 100644
--- a/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/HumanAIController.cs
+++ b/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/HumanAIController.cs
@@ -382,8 +382,13 @@ namespace Barotrauma
             }
             steeringBuffer = Math.Clamp(steeringBuffer, minSteeringBuffer, maxSteeringBuffer);
 
-            AnimController.Crouching = shouldCrouch;
-            CheckCrouching(deltaTime);
+            // in case of somehow AnimController was a null, eg. something removed AnimController in the middle of an update
+            if (AnimController != null) 
+            {
+                AnimController.Crouching = shouldCrouch;
+                CheckCrouching(deltaTime);
+            }
+
             Character.ClearInputs();
             
             if (SortTimer > 0.0f)
@@ -1638,7 +1643,8 @@ namespace Barotrauma
             if (mode == AIObjectiveCombat.CombatMode.None) { return; }
             if (Character.IsDead || Character.IsIncapacitated || Character.Removed) { return; }
             if (!Character.IsBot) { return; }
-            if (ObjectiveManager.Objectives.FirstOrDefault(o => o is AIObjectiveCombat) is AIObjectiveCombat combatObjective)
+            List<AIObjective> ObjectivesLocal = ObjectiveManager.Objectives;
+            if (ObjectivesLocal.FirstOrDefault(o => o is AIObjectiveCombat) is AIObjectiveCombat combatObjective)
             {
                 // Don't replace offensive mode with something else
                 if (combatObjective.Mode == AIObjectiveCombat.CombatMode.Offensive && mode != AIObjectiveCombat.CombatMode.Offensive) { return; }
diff --git a/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/Objectives/AIObjectiveManager.cs b/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/Objectives/AIObjectiveManager.cs
index 83e475c37..ead5b6a87 100644
--- a/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/Objectives/AIObjectiveManager.cs
+++ b/Barotrauma/BarotraumaShared/SharedSource/Characters/AI/Objectives/AIObjectiveManager.cs
@@ -126,7 +126,7 @@ namespace Barotrauma
             }
             else
             {
-                Objectives.RemoveAll(o => o.GetType() == type);
+                Objectives.RemoveAll(o => o?.GetType() == type);
             }
             Objectives.Add(objective);
         }
diff --git a/Barotrauma/BarotraumaShared/SharedSource/Items/Components/Signal/Connection.cs b/Barotrauma/BarotraumaShared/SharedSource/Items/Components/Signal/Connection.cs
index d55150237..37cb33d9c 100644
--- a/Barotrauma/BarotraumaShared/SharedSource/Items/Components/Signal/Connection.cs
+++ b/Barotrauma/BarotraumaShared/SharedSource/Items/Components/Signal/Connection.cs
@@ -345,7 +345,8 @@ namespace Barotrauma.Items.Components
             {
                 Connection recipient = wire.OtherConnection(this);
                 if (recipient == null) { continue; }
-                if (recipient.item == this.item || signal.source?.LastSentSignalRecipients.LastOrDefault() == recipient) { continue; }
+                List<Connection> LastSentSignalRecipientsCopy = signal.source?.LastSentSignalRecipients.ToList();
+                if (recipient.item == this.item || LastSentSignalRecipientsCopy.LastOrDefault() == recipient) { continue; }
 
                 signal.source?.LastSentSignalRecipients.Add(recipient);
 #if CLIENT
diff --git a/Barotrauma/BarotraumaShared/SharedSource/Map/MapEntity.cs b/Barotrauma/BarotraumaShared/SharedSource/Map/MapEntity.cs
index b61d2e68e..fb3723934 100644
--- a/Barotrauma/BarotraumaShared/SharedSource/Map/MapEntity.cs
+++ b/Barotrauma/BarotraumaShared/SharedSource/Map/MapEntity.cs
@@ -816,7 +816,7 @@ namespace Barotrauma
 
             // Gap update (has order dependencies, keep random order but execute sequentially)
             var shuffledGaps = gapList.OrderBy(g => Rand.Int(int.MaxValue)).ToList();
-            Parallel.ForEach(gapList, parallelOptions, gap =>
+            Parallel.ForEach(shuffledGaps, parallelOptions, gap =>
             {
                 PhysicsBodyQueue.IsInParallelContext = true;
                 try
diff --git a/Barotrauma/BarotraumaShared/SharedSource/Screens/GameScreen.cs b/Barotrauma/BarotraumaShared/SharedSource/Screens/GameScreen.cs
index e2fddef7c..be3e4bb12 100644
--- a/Barotrauma/BarotraumaShared/SharedSource/Screens/GameScreen.cs
+++ b/Barotrauma/BarotraumaShared/SharedSource/Screens/GameScreen.cs
@@ -25,7 +25,7 @@ namespace Barotrauma
 
         private static readonly ParallelOptions parallelOptions = new ParallelOptions
         {
-            MaxDegreeOfParallelism = Environment.ProcessorCount * 2,
+            MaxDegreeOfParallelism = Math.Max(4,Environment.ProcessorCount - 1),
         };
 
 #if CLIENT
@@ -259,33 +259,15 @@ namespace Barotrauma
             Character.Controlled?.UpdateLocalCursor(cam);
 
 #elif SERVER
-            Parallel.Invoke(parallelOptions,
-                () => 
-                { 
-                    PhysicsBodyQueue.IsInParallelContext = true;
-                    try
-                    {
-                        if (Level.Loaded != null) Level.Loaded.Update((float)deltaTime, Camera.Instance);
-                    }
-                    finally
-                    {
-                        PhysicsBodyQueue.IsInParallelContext = false;
-                    }
-                },
-                () => 
-                {
-                    PhysicsBodyQueue.IsInParallelContext = true;
-                    try
-                    {
-                        Character.UpdateAll((float)deltaTime, Camera.Instance);
-                    }
-                    finally
-                    {
-                        PhysicsBodyQueue.IsInParallelContext = false;
-                    }
-                }
-            );
-            
+            // DO NOT PARALLELIZE THESE TWO OR IT MAY STUCK HERE
+            // SO FOLLOW THE ORIGINAL SINGLE-THREAD LOGIC STRICTLY
+
+            if (Level.Loaded != null) Level.Loaded.Update((float)deltaTime, Camera.Instance);
+
+            Character.UpdateAll((float)deltaTime, Camera.Instance);
+
+            StatusEffect.UpdateAll((float)deltaTime);
+
             PhysicsBodyQueue.ProcessPendingOperations();
 #endif
 
@@ -310,8 +292,6 @@ namespace Barotrauma
 
             MapEntity.UpdateAll((float)deltaTime, Camera.Instance, parallelOptions);
 
-            StatusEffect.UpdateAll((float)deltaTime);
-
 #endif
 
 #if CLIENT
@@ -321,6 +301,7 @@ namespace Barotrauma
 #endif
             //Character.UpdateAnimAll is not thread-safe and must be executed on the main thread
             Character.UpdateAnimAll((float)deltaTime);
+            PhysicsBodyQueue.ProcessPendingOperations();
 
 #if CLIENT
             Ragdoll.UpdateAll((float)deltaTime, cam);