diff --git a/yt_dlp/downloader/fragment.py b/yt_dlp/downloader/fragment.py
index 1cc99a4e9..e3af140fd 100644
--- a/yt_dlp/downloader/fragment.py
+++ b/yt_dlp/downloader/fragment.py
@@ -329,7 +329,7 @@ def _prepare_external_frag_download(self, ctx):
             'fragment_index': 0,
         })
 
-    def download_and_append_fragments(self, ctx, fragments, info_dict, pack_func=None):
+    def download_and_append_fragments(self, ctx, fragments, info_dict, *, pack_func=None, finish_func=None):
         fragment_retries = self.params.get('fragment_retries', 0)
         is_fatal = (lambda idx: idx == 0) if self.params.get('skip_unavailable_fragments', True) else (lambda _: True)
         if not pack_func:
@@ -424,5 +424,8 @@ def _download_fragment(fragment):
                 if not result:
                     return False
 
+        if finish_func is not None:
+            ctx['dest_stream'].write(finish_func())
+            ctx['dest_stream'].flush()
         self._finish_frag_download(ctx, info_dict)
         return True
diff --git a/yt_dlp/downloader/hls.py b/yt_dlp/downloader/hls.py
index 9cbd5a584..9cfc191cb 100644
--- a/yt_dlp/downloader/hls.py
+++ b/yt_dlp/downloader/hls.py
@@ -260,29 +260,35 @@ def pack_fragment(frag_content, frag_index):
                         block.end += adjust
 
                         dedup_window = extra_state.setdefault('webvtt_dedup_window', [])
-                        cue = block.as_json
 
-                        # skip the cue if an identical one appears
-                        # in the window of potential duplicates
-                        # and prune the window of unviable candidates
+                        ready = []
+
                         i = 0
-                        skip = True
+                        is_new = True
                         while i < len(dedup_window):
-                            window_cue = dedup_window[i]
-                            if window_cue == cue:
-                                break
-                            if window_cue['end'] >= cue['start']:
-                                i += 1
+                            wcue = dedup_window[i]
+                            wblock = webvtt.CueBlock.from_json(wcue)
+                            i += 1
+                            if wblock.hinges(block):
+                                wcue['end'] = block.end
+                                is_new = False
                                 continue
+                            if wblock == block:
+                                is_new = False
+                                continue
+                            if wblock.end > block.start:
+                                continue
+                            ready.append(wblock)
+                            i -= 1
                             del dedup_window[i]
-                        else:
-                            skip = False
 
-                        if skip:
-                            continue
+                        if is_new:
+                            dedup_window.append(block.as_json)
+                        for block in ready:
+                            block.write_into(output)
 
-                        # add the cue to the window
-                        dedup_window.append(cue)
+                        # we only emit cues once they fall out of the duplicate window
+                        continue
                     elif isinstance(block, webvtt.Magic):
                         # take care of MPEG PES timestamp overflow
                         if block.mpegts is None:
@@ -317,6 +323,19 @@ def pack_fragment(frag_content, frag_index):
                     block.write_into(output)
 
                 return output.getvalue().encode('utf-8')
+
+            def fin_fragments():
+                dedup_window = extra_state.get('webvtt_dedup_window')
+                if not dedup_window:
+                    return b''
+
+                output = io.StringIO()
+                for cue in dedup_window:
+                    webvtt.CueBlock.from_json(cue).write_into(output)
+
+                return output.getvalue().encode('utf-8')
+
+            self.download_and_append_fragments(
+                ctx, fragments, info_dict, pack_func=pack_fragment, finish_func=fin_fragments)
         else:
-            pack_fragment = None
-        return self.download_and_append_fragments(ctx, fragments, info_dict, pack_fragment)
+            return self.download_and_append_fragments(ctx, fragments, info_dict)
diff --git a/yt_dlp/webvtt.py b/yt_dlp/webvtt.py
index ef55e6459..eee2a4a2d 100644
--- a/yt_dlp/webvtt.py
+++ b/yt_dlp/webvtt.py
@@ -331,6 +331,26 @@ def as_json(self):
             'settings': self.settings,
         }
 
+    def __eq__(self, other):
+        return self.as_json == other.as_json
+
+    @classmethod
+    def from_json(cls, json):
+        return cls(
+            id=json['id'],
+            start=json['start'],
+            end=json['end'],
+            text=json['text'],
+            settings=json['settings']
+        )
+
+    def hinges(self, other):
+        if self.text != other.text:
+            return False
+        if self.settings != other.settings:
+            return False
+        return self.start <= self.end == other.start <= other.end
+
 
 def parse_fragment(frag_content):
     """