diff --git a/Svelto.ECS/EnginesRoot.Engines.cs b/Svelto.ECS/EnginesRoot.Engines.cs
index 45c4c50..3d0f0ae 100644
--- a/Svelto.ECS/EnginesRoot.Engines.cs
+++ b/Svelto.ECS/EnginesRoot.Engines.cs
@@ -47,10 +47,10 @@ namespace Svelto.ECS
             try
             {
                 if (engine is IReactOnAddAndRemove viewEngine)
-                    CheckEntityViewsEngine(viewEngine, _reactiveEnginesAddRemove);
+                    CheckEntityViewsEngine<IReactOnAddAndRemove>(viewEngine, _reactiveEnginesAddRemove);
                 
                 if (engine is IReactOnSwap viewEngineSwap)
-                    CheckEntityViewsEngine(viewEngineSwap, _reactiveEnginesSwap);
+                    CheckEntityViewsEngine<IReactOnSwap>(viewEngineSwap, _reactiveEnginesSwap);
 
                 _enginesSet.Add(engine);
 
@@ -73,13 +73,13 @@ namespace Svelto.ECS
             }
         }
        
-        void CheckEntityViewsEngine(IEngine engine, Dictionary<Type, FasterList<IEngine>> engines)
+        void CheckEntityViewsEngine<T>(IEngine engine, Dictionary<Type, FasterList<IEngine>> engines)
         {
             var interfaces = engine.GetType().GetInterfaces();
 
             foreach (var interf in interfaces)
             {
-                if (interf.IsGenericTypeEx() && typeof(IReactEngine).IsAssignableFrom(interf))
+                if (interf.IsGenericTypeEx() && typeof(T).IsAssignableFrom(interf))
                 {
                     var genericArguments = interf.GetGenericArgumentsEx();
 
diff --git a/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs b/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs
index 4f40fad..8fc3ade 100644
--- a/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs
+++ b/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs
@@ -126,7 +126,7 @@ namespace Svelto.ECS
             if (_entitiesOperations.TryGetValue((ulong) entitySubmitOperation.fromID, out var entitySubmitedOperation) == true)
             {
                 if (entitySubmitedOperation != entitySubmitOperation)
-                Console.LogError("Only one entity operation per submission is allowed".FastConcat(" entityViewType: ")
+                    throw new ECSException("Only one entity operation per submission is allowed".FastConcat(" entityViewType: ")
                                     .FastConcat(typeof(T).Name)
                                     .FastConcat(" submission type ", entitySubmitOperation.type.ToString(),
                                                 " from ID: ",  entitySubmitOperation.fromID.entityID.ToString())
diff --git a/Svelto.ECS/EnginesRoot.Submission.cs b/Svelto.ECS/EnginesRoot.Submission.cs
index 1ed6b26..a2285f0 100644
--- a/Svelto.ECS/EnginesRoot.Submission.cs
+++ b/Svelto.ECS/EnginesRoot.Submission.cs
@@ -56,7 +56,7 @@ namespace Svelto.ECS
                             }
                             catch (Exception e)
                             {
-                                var str = "Crash while executing Entity Operation"
+                                var str = "Crash while executing Entity Operation "
                                    .FastConcat(entitiesOperations[i].type.ToString());
 #if RELAXED_ECS && !PROFILER
                                 Console.LogException(str.FastConcat(" "