diff --git a/CHANGELOG.md b/CHANGELOG.md
index f84dc790..c0718686 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 ## vX.Y.0 (future)
 
+## v2.20250504.0
+
+Small release with quick workaround fix for issue #4251 (Nil assertion failed).
+
+PR: https://github.com/iv-org/invidious/issues/5263
+
 ## v2.20250314.0
 
 ### Wrap-up
diff --git a/config/config.example.yml b/config/config.example.yml
index 33bda8cb..c4aaf9b8 100644
--- a/config/config.example.yml
+++ b/config/config.example.yml
@@ -90,14 +90,14 @@ db:
 ##
 ## API key for Invidious companion, used for securing the communication
 ## between Invidious and Invidious companion.
-## The size of the key needs to be more or equal to 16.
+## The key needs to be exactly 16 characters long.
 ##
 ## Note: This parameter is mandatory when Invidious companion is enabled
 ## and should be a random string.
 ## Such random string can be generated on linux with the following
 ## command: `pwgen 16 1`
 ##
-## Accepted values: a string
+## Accepted values: a string (of length 16)
 ## Default: <none>
 ##
 #invidious_companion_key: "CHANGE_ME!!"
@@ -921,9 +921,9 @@ default_user_preferences:
   ## Default video quality.
   ##
   ## Accepted values: dash, hd720, medium, small
-  ## Default: hd720
+  ## Default: dash
   ##
-  #quality: hd720
+  #quality: dash
 
   ##
   ## Default dash video quality.
diff --git a/src/invidious/config.cr b/src/invidious/config.cr
index 5fdc687c..471c72f0 100644
--- a/src/invidious/config.cr
+++ b/src/invidious/config.cr
@@ -35,7 +35,7 @@ struct ConfigPreferences
   property max_results : Int32 = 40
   property notifications_only : Bool = false
   property player_style : String = "invidious"
-  property quality : String = "hd720"
+  property quality : String = "dash"
   property quality_dash : String = "auto"
   property default_home : String? = "Popular"
   property feed_menu : Array(String) = ["Popular", "Trending", "Subscriptions", "Playlists", "History"]
diff --git a/src/invidious/frontend/watch_page.cr b/src/invidious/frontend/watch_page.cr
index 2e2f6ad0..15d925e3 100644
--- a/src/invidious/frontend/watch_page.cr
+++ b/src/invidious/frontend/watch_page.cr
@@ -23,10 +23,16 @@ module Invidious::Frontend::WatchPage
       return "<p id=\"download\">#{translate(locale, "Download is disabled")}</p>"
     end
 
+    url = "/download"
+    if (CONFIG.invidious_companion.present?)
+      invidious_companion = CONFIG.invidious_companion.sample
+      url = "#{invidious_companion.public_url}/download?check=#{invidious_companion_encrypt(video.id)}"
+    end
+
     return String.build(4000) do |str|
       str << "<form"
       str << " class=\"pure-form pure-form-stacked\""
-      str << " action='/download'"
+      str << " action='#{url}'"
       str << " method='post'"
       str << " rel='noopener'"
       str << " target='_blank'>"
diff --git a/src/invidious/routes/video_playback.cr b/src/invidious/routes/video_playback.cr
index ce7b43dc..76d929a2 100644
--- a/src/invidious/routes/video_playback.cr
+++ b/src/invidious/routes/video_playback.cr
@@ -31,7 +31,7 @@ module Invidious::Routes::VideoPlayback
     end
 
     # Sanity check, to avoid being used as an open proxy
-    if !host.matches?(/[\w-]+.googlevideo.com/) && !host.matches?(/[\w-]+.c.youtube.com/)
+    if !host.matches?(/[\w-]+\.(?:googlevideo|c\.youtube)\.com/)
       return error_template(400, "Invalid \"host\" parameter.")
     end
 
@@ -47,7 +47,8 @@ module Invidious::Routes::VideoPlayback
 
     # See: https://github.com/iv-org/invidious/issues/3302
     range_header = env.request.headers["Range"]?
-    if range_header.nil?
+    sq = query_params["sq"]?
+    if range_header.nil? && sq.nil?
       range_for_head = query_params["range"]? || "0-640"
       headers["Range"] = "bytes=#{range_for_head}"
     end
diff --git a/src/invidious/routes/watch.cr b/src/invidious/routes/watch.cr
index b3d25e8e..0d55bab7 100644
--- a/src/invidious/routes/watch.cr
+++ b/src/invidious/routes/watch.cr
@@ -311,6 +311,9 @@ module Invidious::Routes::Watch
     if CONFIG.disabled?("downloads")
       return error_template(403, "Administrator has disabled this endpoint.")
     end
+    if CONFIG.invidious_companion.present?
+      return error_template(403, "Downloads should be routed through Companion when present")
+    end
 
     title = env.params.body["title"]? || ""
     video_id = env.params.body["id"]? || ""
@@ -346,13 +349,7 @@ module Invidious::Routes::Watch
       env.params.query["title"] = filename
       env.params.query["local"] = "true"
 
-      if (CONFIG.invidious_companion.present?)
-        video = get_video(video_id, env: env)
-        companion_public_url = env.get("companion_public_url").as(String)
-        return env.redirect "#{companion_public_url}/latest_version?#{env.params.query}"
-      else
-        return Invidious::Routes::VideoPlayback.latest_version(env)
-      end
+      return Invidious::Routes::VideoPlayback.latest_version(env)
     else
       return error_template(400, "Invalid label or itag")
     end
diff --git a/src/invidious/videos/parser.cr b/src/invidious/videos/parser.cr
index f7853ec4..6f9bc565 100644
--- a/src/invidious/videos/parser.cr
+++ b/src/invidious/videos/parser.cr
@@ -109,27 +109,20 @@ def extract_video_info(video_id : String, env : HTTP::Server::Context | Nil = ni
   params["reason"] = JSON::Any.new(reason) if reason
 
   if !CONFIG.invidious_companion.present?
-    new_player_response = nil
-
-    # Don't use Android test suite client if po_token is passed because po_token doesn't
-    # work for Android test suite client.
-    if reason.nil? && CONFIG.po_token.nil?
-      # Fetch the video streams using an Android client in order to get the
-      # decrypted URLs and maybe fix throttling issues (#2194). See the
-      # following issue for an explanation about decrypted URLs:
-      # https://github.com/TeamNewPipe/NewPipeExtractor/issues/562
-      client_config.client_type = YoutubeAPI::ClientType::AndroidTestSuite
-      new_player_response = try_fetch_streaming_data(video_id, client_config, env)
-    end
-
-    # Replace player response and reset reason
-    if !new_player_response.nil?
-      # Preserve captions & storyboard data before replacement
-      new_player_response["storyboards"] = player_response["storyboards"] if player_response["storyboards"]?
-      new_player_response["captions"] = player_response["captions"] if player_response["captions"]?
-
-      player_response = new_player_response
-      params.delete("reason")
+    if player_response["streamingData"]? && player_response.dig?("streamingData", "adaptiveFormats", 0, "url").nil?
+      LOGGER.warn("Missing URLs for adaptive formats, falling back to other YT clients.")
+      players_fallback = [YoutubeAPI::ClientType::WebMobile, YoutubeAPI::ClientType::TvHtml5]
+      players_fallback.each do |player_fallback|
+        client_config.client_type = player_fallback
+        player_fallback_response = try_fetch_streaming_data(video_id, client_config, env)
+        if player_fallback_response && player_fallback_response["streamingData"]? &&
+           player_fallback_response.dig?("streamingData", "adaptiveFormats", 0, "url")
+          streaming_data = player_response["streamingData"].as_h
+          streaming_data["adaptiveFormats"] = player_fallback_response["streamingData"]["adaptiveFormats"]
+          player_response["streamingData"] = JSON::Any.new(streaming_data)
+          break
+        end
+      end
     end
   end