diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index de912f643d..acb595a6d8 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -47,6 +47,9 @@
         per sample.
     *   Fix playback hanging on DASH multi-period streams when CEA-608 subtitles
         are enabled ([#1863](https://github.com/androidx/media/issues/1863)).
+    *   Fix garbled CEA-608 subtitles in MP4 files that incorrectly mark every
+        sample as a sync sample
+        ([#1863](https://github.com/androidx/media/issues/1863)).
 *   Metadata:
 *   Image:
 *   DRM:
diff --git a/libraries/extractor/src/main/java/androidx/media3/extractor/mp4/FragmentedMp4Extractor.java b/libraries/extractor/src/main/java/androidx/media3/extractor/mp4/FragmentedMp4Extractor.java
index 104b54ce66..3f8dd29b53 100644
--- a/libraries/extractor/src/main/java/androidx/media3/extractor/mp4/FragmentedMp4Extractor.java
+++ b/libraries/extractor/src/main/java/androidx/media3/extractor/mp4/FragmentedMp4Extractor.java
@@ -1643,17 +1643,17 @@ public class FragmentedMp4Extractor implements Extractor {
                     : 0);
             nalBuffer.setLimit(unescapedLength);
 
-            if (track.format.maxNumReorderSamples != Format.NO_VALUE
-                && track.format.maxNumReorderSamples != reorderingSeiMessageQueue.getMaxSize()) {
+            if (track.format.maxNumReorderSamples == Format.NO_VALUE) {
+              if (reorderingSeiMessageQueue.getMaxSize() != 0) {
+                reorderingSeiMessageQueue.setMaxSize(0);
+              }
+            } else if (reorderingSeiMessageQueue.getMaxSize()
+                != track.format.maxNumReorderSamples) {
               reorderingSeiMessageQueue.setMaxSize(track.format.maxNumReorderSamples);
             }
             reorderingSeiMessageQueue.add(sampleTimeUs, nalBuffer);
 
-            boolean sampleIsKeyFrameOrEndOfStream =
-                (trackBundle.getCurrentSampleFlags()
-                        & (C.BUFFER_FLAG_KEY_FRAME | C.BUFFER_FLAG_END_OF_STREAM))
-                    != 0;
-            if (sampleIsKeyFrameOrEndOfStream) {
+            if ((trackBundle.getCurrentSampleFlags() & C.BUFFER_FLAG_END_OF_STREAM) != 0) {
               reorderingSeiMessageQueue.flush();
             }
           } else {