diff --git a/modules/mono/csharp_script.cpp b/modules/mono/csharp_script.cpp
index 996e73a4bb..8471083f49 100644
--- a/modules/mono/csharp_script.cpp
+++ b/modules/mono/csharp_script.cpp
@@ -638,33 +638,41 @@ void CSharpLanguage::reload_tool_script(const Ref<Script> &p_script, bool p_soft
 #ifdef TOOLS_ENABLED
 void CSharpLanguage::reload_assemblies_if_needed(bool p_soft_reload) {
 
-	if (gdmono->is_runtime_initialized()) {
+	if (!gdmono->is_runtime_initialized())
+		return;
 
-		GDMonoAssembly *proj_assembly = gdmono->get_project_assembly();
+	GDMonoAssembly *proj_assembly = gdmono->get_project_assembly();
 
-		String name = ProjectSettings::get_singleton()->get("application/config/name");
-		if (name.empty()) {
-			name = "UnnamedProject";
-		}
+	String name = ProjectSettings::get_singleton()->get("application/config/name");
+	if (name.empty()) {
+		name = "UnnamedProject";
+	}
 
-		if (proj_assembly) {
-			String proj_asm_path = proj_assembly->get_path();
+	name += ".dll";
 
-			if (!FileAccess::exists(proj_assembly->get_path())) {
-				// Maybe it wasn't loaded from the default path, so check this as well
-				proj_asm_path = GodotSharpDirs::get_res_temp_assemblies_dir().plus_file(name);
-				if (!FileAccess::exists(proj_asm_path))
-					return; // No assembly to load
-			}
+	if (proj_assembly) {
+		String proj_asm_path = proj_assembly->get_path();
 
-			if (FileAccess::get_modified_time(proj_asm_path) <= proj_assembly->get_modified_time())
-				return; // Already up to date
-		} else {
-			if (!FileAccess::exists(GodotSharpDirs::get_res_temp_assemblies_dir().plus_file(name)))
+		if (!FileAccess::exists(proj_assembly->get_path())) {
+			// Maybe it wasn't loaded from the default path, so check this as well
+			proj_asm_path = GodotSharpDirs::get_res_temp_assemblies_dir().plus_file(name);
+			if (!FileAccess::exists(proj_asm_path))
 				return; // No assembly to load
 		}
+
+		if (FileAccess::get_modified_time(proj_asm_path) <= proj_assembly->get_modified_time())
+			return; // Already up to date
+	} else {
+		if (!FileAccess::exists(GodotSharpDirs::get_res_temp_assemblies_dir().plus_file(name)))
+			return; // No assembly to load
 	}
 
+	if (!gdmono->get_core_api_assembly() && gdmono->metadata_is_api_assembly_invalidated(APIAssembly::API_CORE))
+		return; // The core API assembly to load is invalidated
+
+	if (!gdmono->get_editor_api_assembly() && gdmono->metadata_is_api_assembly_invalidated(APIAssembly::API_EDITOR))
+		return; // The editor API assembly to load is invalidated
+
 #ifndef NO_THREADS
 	lock->lock();
 #endif
@@ -1963,8 +1971,6 @@ Variant CSharpScript::_new(const Variant **p_args, int p_argcount, Variant::Call
 
 ScriptInstance *CSharpScript::instance_create(Object *p_this) {
 
-	ERR_FAIL_COND_V(!valid, NULL);
-
 	if (!tool && !ScriptServer::is_scripting_enabled()) {
 #ifdef TOOLS_ENABLED
 		PlaceHolderScriptInstance *si = memnew(PlaceHolderScriptInstance(CSharpLanguage::get_singleton(), Ref<Script>(this), p_this));
@@ -1981,13 +1987,15 @@ ScriptInstance *CSharpScript::instance_create(Object *p_this) {
 			// The project assembly is not loaded
 			ERR_EXPLAIN("Cannot instance script because the project assembly is not loaded. Script: " + get_path());
 			ERR_FAIL_V(NULL);
+		} else {
+			// The project assembly is loaded, but the class could not found
+			ERR_EXPLAIN("Cannot instance script because the class '" + name + "' could not be found. Script: " + get_path());
+			ERR_FAIL_V(NULL);
 		}
-
-		// The project assembly is loaded, but the class could not found
-		ERR_EXPLAIN("Cannot instance script because the class '" + name + "' could not be found. Script: " + get_path());
-		ERR_FAIL_V(NULL);
 	}
 
+	ERR_FAIL_COND_V(!valid, NULL);
+
 	if (native) {
 		String native_name = native->get_name();
 		if (!ClassDB::is_parent_class(p_this->get_class_name(), native_name)) {
@@ -2040,6 +2048,9 @@ void CSharpScript::set_source_code(const String &p_code) {
 
 bool CSharpScript::has_method(const StringName &p_method) const {
 
+	if (!script_class)
+		return false;
+
 	return script_class->has_fetched_method_unknown_params(p_method);
 }
 
diff --git a/modules/mono/mono_gd/gd_mono_class.cpp b/modules/mono/mono_gd/gd_mono_class.cpp
index e2597a7d42..53d6b7074c 100644
--- a/modules/mono/mono_gd/gd_mono_class.cpp
+++ b/modules/mono/mono_gd/gd_mono_class.cpp
@@ -322,6 +322,12 @@ GDMonoMethod *GDMonoClass::get_method_with_desc(const String &p_description, boo
 	return get_method(method);
 }
 
+void *GDMonoClass::get_method_thunk(const StringName &p_name, int p_params_count) {
+
+	GDMonoMethod *method = get_method(p_name, p_params_count);
+	return method ? method->get_thunk() : NULL;
+}
+
 GDMonoField *GDMonoClass::get_field(const StringName &p_name) {
 
 	Map<StringName, GDMonoField *>::Element *result = fields.find(p_name);
diff --git a/modules/mono/mono_gd/gd_mono_class.h b/modules/mono/mono_gd/gd_mono_class.h
index f81ab84cd0..f4e386549a 100644
--- a/modules/mono/mono_gd/gd_mono_class.h
+++ b/modules/mono/mono_gd/gd_mono_class.h
@@ -133,6 +133,8 @@ public:
 	GDMonoMethod *get_method(MonoMethod *p_raw_method, const StringName &p_name, int p_params_count);
 	GDMonoMethod *get_method_with_desc(const String &p_description, bool p_include_namespace);
 
+	void *get_method_thunk(const StringName &p_name, int p_params_count = 0);
+
 	GDMonoField *get_field(const StringName &p_name);
 	const Vector<GDMonoField *> &get_all_fields();
 
diff --git a/modules/mono/mono_gd/gd_mono_utils.cpp b/modules/mono/mono_gd/gd_mono_utils.cpp
index 7cd922138f..21efd4064a 100644
--- a/modules/mono/mono_gd/gd_mono_utils.cpp
+++ b/modules/mono/mono_gd/gd_mono_utils.cpp
@@ -176,7 +176,7 @@ void update_corlib_cache() {
 
 #ifdef DEBUG_ENABLED
 	CACHE_CLASS_AND_CHECK(System_Diagnostics_StackTrace, GDMono::get_singleton()->get_corlib_assembly()->get_class("System.Diagnostics", "StackTrace"));
-	CACHE_METHOD_THUNK_AND_CHECK(System_Diagnostics_StackTrace, GetFrames, (StackTrace_GetFrames)CACHED_CLASS(System_Diagnostics_StackTrace)->get_method("GetFrames")->get_thunk());
+	CACHE_METHOD_THUNK_AND_CHECK(System_Diagnostics_StackTrace, GetFrames, (StackTrace_GetFrames)CACHED_CLASS(System_Diagnostics_StackTrace)->get_method_thunk("GetFrames"));
 	CACHE_METHOD_AND_CHECK(System_Diagnostics_StackTrace, ctor_bool, CACHED_CLASS(System_Diagnostics_StackTrace)->get_method_with_desc("System.Diagnostics.StackTrace:.ctor(bool)", true));
 	CACHE_METHOD_AND_CHECK(System_Diagnostics_StackTrace, ctor_Exception_bool, CACHED_CLASS(System_Diagnostics_StackTrace)->get_method_with_desc("System.Diagnostics.StackTrace:.ctor(System.Exception,bool)", true));
 #endif
@@ -234,16 +234,16 @@ void update_godot_api_cache() {
 	CACHE_FIELD_AND_CHECK(NodePath, ptr, CACHED_CLASS(NodePath)->get_field(BINDINGS_PTR_FIELD));
 	CACHE_FIELD_AND_CHECK(RID, ptr, CACHED_CLASS(RID)->get_field(BINDINGS_PTR_FIELD));
 
-	CACHE_METHOD_THUNK_AND_CHECK(Array, GetPtr, (Array_GetPtr)GODOT_API_CLASS(Array)->get_method("GetPtr", 0)->get_thunk());
-	CACHE_METHOD_THUNK_AND_CHECK(Dictionary, GetPtr, (Dictionary_GetPtr)GODOT_API_CLASS(Dictionary)->get_method("GetPtr", 0)->get_thunk());
-	CACHE_METHOD_THUNK_AND_CHECK(MarshalUtils, IsArrayGenericType, (IsArrayGenericType)GODOT_API_CLASS(MarshalUtils)->get_method("IsArrayGenericType", 1)->get_thunk());
-	CACHE_METHOD_THUNK_AND_CHECK(MarshalUtils, IsDictionaryGenericType, (IsDictionaryGenericType)GODOT_API_CLASS(MarshalUtils)->get_method("IsDictionaryGenericType", 1)->get_thunk());
-	CACHE_METHOD_THUNK_AND_CHECK(SignalAwaiter, SignalCallback, (SignalAwaiter_SignalCallback)GODOT_API_CLASS(SignalAwaiter)->get_method("SignalCallback", 1)->get_thunk());
-	CACHE_METHOD_THUNK_AND_CHECK(SignalAwaiter, FailureCallback, (SignalAwaiter_FailureCallback)GODOT_API_CLASS(SignalAwaiter)->get_method("FailureCallback", 0)->get_thunk());
-	CACHE_METHOD_THUNK_AND_CHECK(GodotTaskScheduler, Activate, (GodotTaskScheduler_Activate)GODOT_API_CLASS(GodotTaskScheduler)->get_method("Activate", 0)->get_thunk());
+	CACHE_METHOD_THUNK_AND_CHECK(Array, GetPtr, (Array_GetPtr)GODOT_API_CLASS(Array)->get_method_thunk("GetPtr", 0));
+	CACHE_METHOD_THUNK_AND_CHECK(Dictionary, GetPtr, (Dictionary_GetPtr)GODOT_API_CLASS(Dictionary)->get_method_thunk("GetPtr", 0));
+	CACHE_METHOD_THUNK_AND_CHECK(MarshalUtils, IsArrayGenericType, (IsArrayGenericType)GODOT_API_CLASS(MarshalUtils)->get_method_thunk("IsArrayGenericType", 1));
+	CACHE_METHOD_THUNK_AND_CHECK(MarshalUtils, IsDictionaryGenericType, (IsDictionaryGenericType)GODOT_API_CLASS(MarshalUtils)->get_method_thunk("IsDictionaryGenericType", 1));
+	CACHE_METHOD_THUNK_AND_CHECK(SignalAwaiter, SignalCallback, (SignalAwaiter_SignalCallback)GODOT_API_CLASS(SignalAwaiter)->get_method_thunk("SignalCallback", 1));
+	CACHE_METHOD_THUNK_AND_CHECK(SignalAwaiter, FailureCallback, (SignalAwaiter_FailureCallback)GODOT_API_CLASS(SignalAwaiter)->get_method_thunk("FailureCallback", 0));
+	CACHE_METHOD_THUNK_AND_CHECK(GodotTaskScheduler, Activate, (GodotTaskScheduler_Activate)GODOT_API_CLASS(GodotTaskScheduler)->get_method_thunk("Activate", 0));
 
 #ifdef DEBUG_ENABLED
-	CACHE_METHOD_THUNK_AND_CHECK(DebuggingUtils, GetStackFrameInfo, (DebugUtils_StackFrameInfo)GODOT_API_CLASS(DebuggingUtils)->get_method("GetStackFrameInfo", 4)->get_thunk());
+	CACHE_METHOD_THUNK_AND_CHECK(DebuggingUtils, GetStackFrameInfo, (DebugUtils_StackFrameInfo)GODOT_API_CLASS(DebuggingUtils)->get_method_thunk("GetStackFrameInfo", 4));
 #endif
 
 	// TODO Move to CSharpLanguage::init()