diff --git a/Tools/BiblioTech/CodexChecking/CodexTwoWayChecker.cs b/Tools/BiblioTech/CodexChecking/CodexTwoWayChecker.cs
index 83175803..ac83ccd9 100644
--- a/Tools/BiblioTech/CodexChecking/CodexTwoWayChecker.cs
+++ b/Tools/BiblioTech/CodexChecking/CodexTwoWayChecker.cs
@@ -37,7 +37,7 @@ namespace BiblioTech.CodexChecking
         public async Task StartDownloadCheck(ICheckResponseHandler handler, ulong userId)
         {
             var check = repo.GetOrCreate(userId).DownloadCheck;
-            if (string.IsNullOrEmpty(check.UniqueData))
+            if (IsUniqueDataStale(check))
             {
                 check.UniqueData = GenerateUniqueData();
                 repo.SaveChanges();
@@ -69,7 +69,7 @@ namespace BiblioTech.CodexChecking
         public async Task StartUploadCheck(ICheckResponseHandler handler, ulong userId)
         {
             var check = repo.GetOrCreate(userId).UploadCheck;
-            if (string.IsNullOrEmpty(check.UniqueData))
+            if (IsUniqueDataStale(check))
             {
                 check.UniqueData = GenerateUniqueData();
                 repo.SaveChanges();
@@ -111,6 +111,15 @@ namespace BiblioTech.CodexChecking
             return $"{RandomBusyMessage.Get().Substring(5)}{RandomUtils.GenerateRandomString(12)}";
         }
 
+        private bool IsUniqueDataStale(TransferCheck check)
+        {
+            var expiry = DateTime.UtcNow - TimeSpan.FromMinutes(10.0);
+
+            return
+                string.IsNullOrEmpty(check.UniqueData) ||
+                check.CompletedUtc < expiry;
+        }
+
         private string UploadData(string uniqueData)
         {
             var filePath = Path.Combine(config.ChecksDataPath, Guid.NewGuid().ToString());