diff --git a/server/utils/ffmpegHelpers.js b/server/utils/ffmpegHelpers.js
index ecc86f454..80832cc77 100644
--- a/server/utils/ffmpegHelpers.js
+++ b/server/utils/ffmpegHelpers.js
@@ -295,18 +295,19 @@ module.exports.writeFFMetadataFile = writeFFMetadataFile
  * @returns {Promise<void>} A promise that resolves if the operation is successful, rejects otherwise.
  */
 async function addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataFilePath, track, mimeType, progressCB = null, ffmpeg = Ffmpeg(), copyFunc = copyToExisting) {
+  const isMp4 = mimeType === 'audio/mp4'
+  const isMp3 = mimeType === 'audio/mpeg'
+
   const audioFileDir = Path.dirname(audioFilePath)
   const audioFileExt = Path.extname(audioFilePath)
   const audioFileBaseName = Path.basename(audioFilePath, audioFileExt)
   const tempFilePath = filePathToPOSIX(Path.join(audioFileDir, `${audioFileBaseName}.tmp${audioFileExt}`))
 
-  const isMp4 = mimeType === 'audio/mp4' || audioFileExt.toLowerCase() === '.m4b'
-  const isMp3 = mimeType === 'audio/mpeg'
-
   return new Promise((resolve, reject) => {
     ffmpeg.input(audioFilePath).input(metadataFilePath).outputOptions([
       '-map 0:a', // map audio stream from input file
-      '-map_metadata 1', // map metadata tags from metadata file (contains all desired metadata)
+      '-map_metadata 1', // map metadata tags from metadata file first
+      '-map_metadata 0', // add additional metadata tags from input file
       '-map_chapters 1', // map chapters from metadata file
       '-c copy' // copy streams
     ])
@@ -317,8 +318,7 @@ async function addCoverAndMetadataToFile(audioFilePath, coverFilePath, metadataF
 
     if (isMp4) {
       ffmpeg.outputOptions([
-        '-f mp4', // force output format to mp4
-        '-movflags use_metadata_tags' // preserve custom tags like AUDIBLE_ASIN
+        '-f mp4' // force output format to mp4
       ])
     } else if (isMp3) {
       ffmpeg.outputOptions([
@@ -414,8 +414,7 @@ function getFFMetadataObject(libraryItem, audioFilesLength) {
     copyright: libraryItem.media.publisher,
     publisher: libraryItem.media.publisher, // mp3 only
     TRACKTOTAL: `${audioFilesLength}`, // mp3 only
-    grouping: libraryItem.media.series?.map((s) => s.name + (s.bookSeries.sequence ? ` #${s.bookSeries.sequence}` : '')).join('; '),
-    AUDIBLE_ASIN: libraryItem.media.asin // Audible ASIN tag for m4b/mp4 files
+    grouping: libraryItem.media.series?.map((s) => s.name + (s.bookSeries.sequence ? ` #${s.bookSeries.sequence}` : '')).join('; ')
   }
   Object.keys(ffmetadata).forEach((key) => {
     if (!ffmetadata[key]) {
diff --git a/test/server/utils/ffmpegHelpers.test.js b/test/server/utils/ffmpegHelpers.test.js
index 8f2d10bcc..95a2c585b 100644
--- a/test/server/utils/ffmpegHelpers.test.js
+++ b/test/server/utils/ffmpegHelpers.test.js
@@ -120,7 +120,7 @@ describe('addCoverAndMetadataToFile', () => {
     expect(ffmpegStub.input.getCall(2).args[0]).to.equal(coverFilePath)
 
     expect(ffmpegStub.outputOptions.callCount).to.equal(4)
-    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_chapters 1', '-c copy'])
+    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_metadata 0', '-map_chapters 1', '-c copy'])
     expect(ffmpegStub.outputOptions.getCall(1).args[0]).to.deep.equal(['-metadata track=1'])
     expect(ffmpegStub.outputOptions.getCall(2).args[0]).to.deep.equal(['-id3v2_version 3'])
     expect(ffmpegStub.outputOptions.getCall(3).args[0]).to.deep.equal(['-map 2:v', '-disposition:v:0 attached_pic', '-metadata:s:v', 'title=Cover', '-metadata:s:v', 'comment=Cover'])
@@ -153,7 +153,7 @@ describe('addCoverAndMetadataToFile', () => {
     expect(ffmpegStub.input.getCall(1).args[0]).to.equal(metadataFilePath)
 
     expect(ffmpegStub.outputOptions.callCount).to.equal(4)
-    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_chapters 1', '-c copy'])
+    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_metadata 0', '-map_chapters 1', '-c copy'])
     expect(ffmpegStub.outputOptions.getCall(1).args[0]).to.deep.equal(['-metadata track=1'])
     expect(ffmpegStub.outputOptions.getCall(2).args[0]).to.deep.equal(['-id3v2_version 3'])
     expect(ffmpegStub.outputOptions.getCall(3).args[0]).to.deep.equal(['-map 0:v?'])
@@ -195,7 +195,7 @@ describe('addCoverAndMetadataToFile', () => {
     expect(ffmpegStub.input.getCall(2).args[0]).to.equal(coverFilePath)
 
     expect(ffmpegStub.outputOptions.callCount).to.equal(4)
-    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_chapters 1', '-c copy'])
+    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_metadata 0', '-map_chapters 1', '-c copy'])
     expect(ffmpegStub.outputOptions.getCall(1).args[0]).to.deep.equal(['-metadata track=1'])
     expect(ffmpegStub.outputOptions.getCall(2).args[0]).to.deep.equal(['-id3v2_version 3'])
     expect(ffmpegStub.outputOptions.getCall(3).args[0]).to.deep.equal(['-map 2:v', '-disposition:v:0 attached_pic', '-metadata:s:v', 'title=Cover', '-metadata:s:v', 'comment=Cover'])
@@ -227,9 +227,9 @@ describe('addCoverAndMetadataToFile', () => {
     expect(ffmpegStub.input.getCall(2).args[0]).to.equal(coverFilePath)
 
     expect(ffmpegStub.outputOptions.callCount).to.equal(4)
-    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_chapters 1', '-c copy'])
+    expect(ffmpegStub.outputOptions.getCall(0).args[0]).to.deep.equal(['-map 0:a', '-map_metadata 1', '-map_metadata 0', '-map_chapters 1', '-c copy'])
     expect(ffmpegStub.outputOptions.getCall(1).args[0]).to.deep.equal(['-metadata track=1'])
-    expect(ffmpegStub.outputOptions.getCall(2).args[0]).to.deep.equal(['-f mp4', '-movflags use_metadata_tags'])
+    expect(ffmpegStub.outputOptions.getCall(2).args[0]).to.deep.equal(['-f mp4'])
     expect(ffmpegStub.outputOptions.getCall(3).args[0]).to.deep.equal(['-map 2:v', '-disposition:v:0 attached_pic', '-metadata:s:v', 'title=Cover', '-metadata:s:v', 'comment=Cover'])
 
     expect(ffmpegStub.output.calledOnce).to.be.true