diff --git a/API.Benchmark/API.Benchmark.csproj b/API.Benchmark/API.Benchmark.csproj
index 38ec425fe..d6fd4eb9f 100644
--- a/API.Benchmark/API.Benchmark.csproj
+++ b/API.Benchmark/API.Benchmark.csproj
@@ -26,5 +26,10 @@
         <CopyToOutputDirectory>Always</CopyToOutputDirectory>
       </Content>
     </ItemGroup>
+    <ItemGroup>
+      <None Update="Data\AesopsFables.epub">
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </None>
+    </ItemGroup>
 
 </Project>
diff --git a/API.Tests/Data/Aesops Fables/AesopsFables.epub b/API.Benchmark/Data/AesopsFables.epub
similarity index 100%
rename from API.Tests/Data/Aesops Fables/AesopsFables.epub
rename to API.Benchmark/Data/AesopsFables.epub
diff --git a/API.Benchmark/KoreaderHashBenchmark.cs b/API.Benchmark/KoreaderHashBenchmark.cs
new file mode 100644
index 000000000..c0abfd2ad
--- /dev/null
+++ b/API.Benchmark/KoreaderHashBenchmark.cs
@@ -0,0 +1,41 @@
+using API.Helpers.Builders;
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Order;
+using System;
+using API.Entities.Enums;
+
+namespace API.Benchmark
+{
+    [StopOnFirstError]
+    [MemoryDiagnoser]
+    [RankColumn]
+    [Orderer(SummaryOrderPolicy.FastestToSlowest)]
+    [SimpleJob(launchCount: 1, warmupCount: 5, invocationCount: 20)]
+    public class KoreaderHashBenchmark
+    {
+        private const string sourceEpub = "./Data/AesopsFables.epub";
+
+        [Benchmark(Baseline = true)]
+        public void TestBuildManga_baseline()
+        {
+            var file = new MangaFileBuilder(sourceEpub, MangaFormat.Epub)
+                .Build();
+            if (file == null)
+            {
+                throw new Exception("Failed to build manga file");
+            }
+        }
+
+        [Benchmark]
+        public void TestBuildManga_withHash()
+        {
+            var file = new MangaFileBuilder(sourceEpub, MangaFormat.Epub)
+                .WithHash()
+                .Build();
+            if (file == null)
+            {
+                throw new Exception("Failed to build manga file");
+            }
+        }
+    }
+}
diff --git a/API/Controllers/KoreaderController.cs b/API/Controllers/KoreaderController.cs
index ec87f83f1..8ad9ca0e5 100644
--- a/API/Controllers/KoreaderController.cs
+++ b/API/Controllers/KoreaderController.cs
@@ -78,11 +78,20 @@ public class KoreaderController : BaseApiController
     [HttpGet("{apiKey}/syncs/progress/{ebookHash}")]
     public async Task<ActionResult<KoreaderBookDto>> GetProgress(string apiKey, string ebookHash)
     {
-        var userId = await GetUserId(apiKey);
-        var response = await _koreaderService.GetProgress(ebookHash, userId);
-        _logger.LogDebug("Koreader response progress: {Progress}", response.Progress);
+        try
+        {
+            var userId = await GetUserId(apiKey);
+            var response = await _koreaderService.GetProgress(ebookHash, userId);
+            _logger.LogDebug("Koreader response progress: {Progress}", response.Progress);
 
-        return Ok(response);
+            return Ok(response);
+        }
+        catch (KavitaException ex)
+        {
+            return BadRequest(ex.Message);
+        }
+
+        return BadRequest();
     }
 
     private async Task<int> GetUserId(string apiKey)
diff --git a/API/Helpers/Builders/KoreaderBookDtoBuilder.cs b/API/Helpers/Builders/KoreaderBookDtoBuilder.cs
index 64c7adf49..fd701b5e2 100644
--- a/API/Helpers/Builders/KoreaderBookDtoBuilder.cs
+++ b/API/Helpers/Builders/KoreaderBookDtoBuilder.cs
@@ -1,3 +1,5 @@
+using System.Security.Cryptography;
+using System.Text;
 using API.DTOs.Koreader;
 
 namespace API.Helpers.Builders;
@@ -36,7 +38,9 @@ public class KoreaderBookDtoBuilder : IEntityBuilder<KoreaderBookDto>
 
     public KoreaderBookDtoBuilder WithDeviceId(string installId, int userId)
     {
-        _dto.Device_id = installId;
+        using var sha256 = SHA256.Create();
+        var hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(installId + userId));
+        _dto.Device_id = hash.ToString();
         return this;
     }
 }
diff --git a/API/Services/KoreaderService.cs b/API/Services/KoreaderService.cs
index 1ed5ebbe5..fbb51e2ac 100644
--- a/API/Services/KoreaderService.cs
+++ b/API/Services/KoreaderService.cs
@@ -4,6 +4,7 @@ using API.DTOs.Koreader;
 using API.DTOs.Progress;
 using API.Helpers;
 using API.Helpers.Builders;
+using Kavita.Common;
 using Microsoft.Extensions.Logging;
 
 namespace API.Services;
@@ -20,12 +21,14 @@ public class KoreaderService : IKoreaderService
 {
     private readonly IReaderService _readerService;
     private readonly IUnitOfWork _unitOfWork;
+    private readonly ILocalizationService _localizationService;
     private readonly ILogger<KoreaderService> _logger;
 
-    public KoreaderService(IReaderService readerService, IUnitOfWork unitOfWork, ILogger<KoreaderService> logger)
+    public KoreaderService(IReaderService readerService, IUnitOfWork unitOfWork, ILocalizationService localizationService, ILogger<KoreaderService> logger)
     {
         _readerService = readerService;
         _unitOfWork = unitOfWork;
+        _localizationService = localizationService;
         _logger = logger;
     }
 
@@ -43,10 +46,17 @@ public class KoreaderService : IKoreaderService
         var userProgressDto = await _unitOfWork.AppUserProgressRepository.GetUserProgressDtoAsync(file.ChapterId, userId);
         if (userProgressDto == null)
         {
-            // TODO: Handle this case
+            var chapterDto = await _unitOfWork.ChapterRepository.GetChapterDtoAsync(file.ChapterId);
+            if (chapterDto == null) return;
+
+            var volumeDto = await _unitOfWork.VolumeRepository.GetVolumeByIdAsync(chapterDto.VolumeId);
+            if (volumeDto == null) return;
+
             userProgressDto = new ProgressDto()
             {
                 ChapterId = file.ChapterId,
+                VolumeId = chapterDto.VolumeId,
+                SeriesId = volumeDto.SeriesId,
             };
         }
         // Update the bookScrollId if possible
@@ -68,15 +78,14 @@ public class KoreaderService : IKoreaderService
 
         var file = await _unitOfWork.MangaFileRepository.GetByKoreaderHash(bookHash);
 
-        // TODO: How do we handle when file isn't found by hash?
-        if (file == null) return builder.Build();
+        if (file == null) throw new KavitaException(await _localizationService.Translate(userId, "file-missing"));
 
         var progressDto = await _unitOfWork.AppUserProgressRepository.GetUserProgressDtoAsync(file.ChapterId, userId);
         var koreaderProgress = KoreaderHelper.GetKoreaderPosition(progressDto);
 
         return builder.WithProgress(koreaderProgress)
             .WithPercentage(progressDto?.PageNum, file.Pages)
-            .WithDeviceId(settingsDto.InstallId, userId) // TODO: Should we generate a hash for UserId + InstallId so that this DeviceId is unique to the user on the server?
+            .WithDeviceId(settingsDto.InstallId, userId)
             .Build();
     }
 }
diff --git a/UI/Web/src/environments/environment.ts b/UI/Web/src/environments/environment.ts
index e1d9c819c..55758b792 100644
--- a/UI/Web/src/environments/environment.ts
+++ b/UI/Web/src/environments/environment.ts
@@ -3,7 +3,7 @@
 // The list of file replacements can be found in `angular.json`.
 
 // const IP = 'localhost';
-const IP = '10.10.30.215';
+const IP = 'localhost';
 
 export const environment = {
   production: false,