diff --git a/Runtime/Client/EndPointClass.cs b/Runtime/Client/EndPointClass.cs
index 0aab85fc..f266daf0 100644
--- a/Runtime/Client/EndPointClass.cs
+++ b/Runtime/Client/EndPointClass.cs
@@ -27,22 +27,50 @@ public EndPointClass(string endPoint, LootLockerHTTPMethod httpMethod, LootLocke
 
         public string WithPathParameter(object arg0)
         {
-            return string.Format(endPoint, WebUtility.UrlEncode(arg0.ToString()));
+            try {
+                return string.Format(endPoint, WebUtility.UrlEncode(arg0?.ToString() ?? "null"));
+            }
+            catch (FormatException e)
+            {
+                LootLockerLogger.Log($"Error formatting endpoint \"{endPoint}\" with path parameter \"{WebUtility.UrlEncode(arg0?.ToString() ?? "null")}\": {e}", LootLockerLogger.LogLevel.Error);
+                return endPoint;
+            }
         }
 
         public string WithPathParameters(object arg0, object arg1)
         {
-            return string.Format(endPoint, WebUtility.UrlEncode(arg0.ToString()), WebUtility.UrlEncode(arg1.ToString()));
+            try {
+                return string.Format(endPoint, WebUtility.UrlEncode(arg0?.ToString() ?? "null"), WebUtility.UrlEncode(arg1?.ToString() ?? "null"));
+            }
+            catch (FormatException e)
+            {
+                LootLockerLogger.Log($"Error formatting endpoint \"{endPoint}\" with path parameters \"{WebUtility.UrlEncode(arg0?.ToString() ?? "null")}\", \"{WebUtility.UrlEncode(arg1?.ToString() ?? "null")}\": {e}", LootLockerLogger.LogLevel.Error);
+                return endPoint;
+            }
         }
 
         public string WithPathParameters(object arg0, object arg1, object arg2)
         {
-            return string.Format(endPoint, WebUtility.UrlEncode(arg0.ToString()), WebUtility.UrlEncode(arg1.ToString()), WebUtility.UrlEncode(arg2.ToString()));
+            try {
+                return string.Format(endPoint, WebUtility.UrlEncode(arg0?.ToString() ?? "null"), WebUtility.UrlEncode(arg1?.ToString() ?? "null"), WebUtility.UrlEncode(arg2?.ToString() ?? "null"));
+            }
+            catch (FormatException e)
+            {
+                LootLockerLogger.Log($"Error formatting endpoint \"{endPoint}\" with path parameters \"{WebUtility.UrlEncode(arg0?.ToString() ?? "null")}\", \"{WebUtility.UrlEncode(arg1?.ToString() ?? "null")}\", \"{WebUtility.UrlEncode(arg2?.ToString() ?? "null")}\": {e}", LootLockerLogger.LogLevel.Error);
+                return endPoint;
+            }
         }
 
         public string WithPathParameters(object arg0, object arg1, object arg2, object arg3)
         {
-            return string.Format(endPoint, WebUtility.UrlEncode(arg0.ToString()), WebUtility.UrlEncode(arg1.ToString()), WebUtility.UrlEncode(arg2.ToString()), WebUtility.UrlEncode(arg3.ToString()));
+            try {
+                return string.Format(endPoint, WebUtility.UrlEncode(arg0?.ToString() ?? "null"), WebUtility.UrlEncode(arg1?.ToString() ?? "null"), WebUtility.UrlEncode(arg2?.ToString() ?? "null"), WebUtility.UrlEncode(arg3?.ToString() ?? "null"));
+            }
+            catch (FormatException e)
+            {
+                LootLockerLogger.Log($"Error formatting endpoint \"{endPoint}\" with path parameters \"{WebUtility.UrlEncode(arg0?.ToString() ?? "null")}\", \"{WebUtility.UrlEncode(arg1?.ToString() ?? "null")}\", \"{WebUtility.UrlEncode(arg2?.ToString() ?? "null")}\", \"{WebUtility.UrlEncode(arg3?.ToString() ?? "null")}\": {e}", LootLockerLogger.LogLevel.Error);
+                return endPoint;
+            }
         }
     }
 }
diff --git a/Runtime/Client/LootLockerHTTPClient.cs b/Runtime/Client/LootLockerHTTPClient.cs
index 96a9ff8d..5157db3f 100644
--- a/Runtime/Client/LootLockerHTTPClient.cs
+++ b/Runtime/Client/LootLockerHTTPClient.cs
@@ -566,8 +566,11 @@ private void CallListenersAndMarkDone(LootLockerHTTPExecutionQueueItem execution
             executionItem.Done = true;
             response.requestContext = new LootLockerRequestContext(executionItem.RequestData.ForPlayerWithUlid, executionItem.RequestData.RequestStartTime);
             executionItem.Response = response;
+            if (!CompletedRequestIDs.Contains(executionItem.RequestData.RequestId)) 
+            {
+                CompletedRequestIDs.Add(executionItem.RequestData.RequestId);
+            }
             executionItem.RequestData.CallListenersWithResult(response);
-            CompletedRequestIDs.Add(executionItem.RequestData.RequestId);
         }
 
         private IEnumerator RefreshSession(string refreshForPlayerUlid, string forExecutionItemId, Action<LootLockerSessionResponse, string, string> onSessionRefreshedCallback)
diff --git a/Runtime/Client/LootLockerHttpRequestData.cs b/Runtime/Client/LootLockerHttpRequestData.cs
index 51d4976b..4bc2cb99 100644
--- a/Runtime/Client/LootLockerHttpRequestData.cs
+++ b/Runtime/Client/LootLockerHttpRequestData.cs
@@ -87,7 +87,14 @@ public void CallListenersWithResult(LootLockerResponse response)
         {
             foreach(var listener in Listeners)
             {
-                listener?.Invoke(response);
+                try
+                {
+                    listener?.Invoke(response);
+                }
+                catch (Exception e)
+                {
+                    LootLockerLogger.Log($"Exception thrown in HTTP request listener for request id {RequestId}. Exception was: {e}.", LootLockerLogger.LogLevel.Error);
+                }
             }
             HaveListenersBeenInvoked = true;
         }
diff --git a/Runtime/Game/Utilities/LootLockerHttpUtilities.cs b/Runtime/Game/Utilities/LootLockerHttpUtilities.cs
index 5881d8a6..1f2a9c97 100644
--- a/Runtime/Game/Utilities/LootLockerHttpUtilities.cs
+++ b/Runtime/Game/Utilities/LootLockerHttpUtilities.cs
@@ -59,7 +59,7 @@ public string Build()
 
             foreach (KeyValuePair<string, string> pair in _queryParams)
             {
-                if (string.IsNullOrEmpty(pair.Value))
+                if (string.IsNullOrEmpty(pair.Key) || string.IsNullOrEmpty(pair.Value))
                     continue;
 
                 if (query.Length > 1)