diff --git a/async_substrate_interface/async_substrate.py b/async_substrate_interface/async_substrate.py
index 5706660..cad2fae 100644
--- a/async_substrate_interface/async_substrate.py
+++ b/async_substrate_interface/async_substrate.py
@@ -274,15 +274,14 @@ async def process_events(self):
                     has_transaction_fee_paid_event = True
 
             # Process other events
+            possible_success = False
             for event in await self.triggered_events:
                 # Check events
                 if (
                     event["event"]["module_id"] == "System"
                     and event["event"]["event_id"] == "ExtrinsicSuccess"
                 ):
-                    if self.__error_message is None:
-                        self.__is_success = True
-                        self.__error_message = None
+                    possible_success = True
 
                     if "dispatch_info" in event["event"]["attributes"]:
                         self.__weight = event["event"]["attributes"]["dispatch_info"][
@@ -299,6 +298,7 @@ async def process_events(self):
                     event["event"]["module_id"] == "MevShield"
                     and event["event"]["event_id"] == "DecryptedRejected"
                 ):
+                    possible_success = False
                     self.__is_success = False
 
                     if event["event"]["module_id"] == "System":
@@ -307,9 +307,13 @@ async def process_events(self):
                         self.__weight = dispatch_info["weight"]
                     else:
                         # MEV shield extrinsics
-                        dispatch_info = event["event"]["attributes"]["reason"]["post_info"]
+                        dispatch_info = event["event"]["attributes"]["reason"][
+                            "post_info"
+                        ]
                         dispatch_error = event["event"]["attributes"]["reason"]["error"]
-                        self.__weight = event["event"]["attributes"]["reason"]["post_info"]["actual_weight"]
+                        self.__weight = event["event"]["attributes"]["reason"][
+                            "post_info"
+                        ]["actual_weight"]
 
                     if "Module" in dispatch_error:
                         if isinstance(dispatch_error["Module"], tuple):
@@ -375,6 +379,10 @@ async def process_events(self):
                         and event["event"]["event_id"] == "Deposit"
                     ):
                         self.__total_fee_amount += event.value["attributes"]["amount"]
+            if possible_success is True and self.__error_message is None:
+                # we delay the positive setting of the __is_success flag until we have finished iteration of the
+                # events and have ensured nothing has set an error message
+                self.__is_success = True
 
     @property
     async def is_success(self) -> bool:
diff --git a/async_substrate_interface/sync_substrate.py b/async_substrate_interface/sync_substrate.py
index c175c1f..bd80d36 100644
--- a/async_substrate_interface/sync_substrate.py
+++ b/async_substrate_interface/sync_substrate.py
@@ -235,14 +235,14 @@ def process_events(self):
                     has_transaction_fee_paid_event = True
 
             # Process other events
+            possible_success = False
             for event in self.triggered_events:
                 # Check events
                 if (
                     event["event"]["module_id"] == "System"
                     and event["event"]["event_id"] == "ExtrinsicSuccess"
                 ):
-                    self.__is_success = True
-                    self.__error_message = None
+                    possible_success = True
 
                     if "dispatch_info" in event["event"]["attributes"]:
                         self.__weight = event["event"]["attributes"]["dispatch_info"][
@@ -255,13 +255,26 @@ def process_events(self):
                 elif (
                     event["event"]["module_id"] == "System"
                     and event["event"]["event_id"] == "ExtrinsicFailed"
+                ) or (
+                    event["event"]["module_id"] == "MevShield"
+                    and event["event"]["event_id"] == "DecryptedRejected"
                 ):
+                    possible_success = False
                     self.__is_success = False
 
-                    dispatch_info = event["event"]["attributes"]["dispatch_info"]
-                    dispatch_error = event["event"]["attributes"]["dispatch_error"]
-
-                    self.__weight = dispatch_info["weight"]
+                    if event["event"]["module_id"] == "System":
+                        dispatch_info = event["event"]["attributes"]["dispatch_info"]
+                        dispatch_error = event["event"]["attributes"]["dispatch_error"]
+                        self.__weight = dispatch_info["weight"]
+                    else:
+                        # MEV shield extrinsics
+                        dispatch_info = event["event"]["attributes"]["reason"][
+                            "post_info"
+                        ]
+                        dispatch_error = event["event"]["attributes"]["reason"]["error"]
+                        self.__weight = event["event"]["attributes"]["reason"][
+                            "post_info"
+                        ]["actual_weight"]
 
                     if "Module" in dispatch_error:
                         if isinstance(dispatch_error["Module"], tuple):
@@ -319,6 +332,10 @@ def process_events(self):
                         and event["event"]["event_id"] == "Deposit"
                     ):
                         self.__total_fee_amount += event.value["attributes"]["amount"]
+            if possible_success is True and self.__error_message is None:
+                # we delay the positive setting of the __is_success flag until we have finished iteration of the
+                # events and have ensured nothing has set an error message
+                self.__is_success = True
 
     @property
     def is_success(self) -> bool: