Youtube Data API v3 PlaylistItems update not worki

Recently, the youtube.playlistItems.list doesn't fetch a playlist item that is suitable for the youtube.playlistItems.update when listing the watchLater playlist. Its works perfectly for playlist that aren't under the relatedPlaylists category of a channel. (e.g. History, favourite, likes etc.)

My list response looks like this:

{
 "items": [
  {
   "id": "V0xWWlh5N2JrM0JSTjAtcDJVUmdjc3JRLjZCM0UwMDFFNUU3NzYzNjc=",
   "snippet": {
    "publishedAt": "2016-03-21T19:04:22.000Z",
    "title": "One Word - Episode 38: Skin Tone (Black Women)",
    .
    .
    .
    "channelTitle": "Ryan Carter",
    "playlistId": "WLVZXy7bk3BRN0-p2URgcsrQ",
    "position": 0,
    "resourceId": {
     "kind": "youtube#video",
     "videoId": "0gYgzN6B0y4"
    }
   }
  },

But when I use those values:

PUT https://www.googleapis.com/youtube/v3/playlistItems?part=snippet%2Cid&key={YOUR_API_KEY}

{
 "id": "V0xWWlh5N2JrM0JSTjAtcDJVUmdjc3JRLjZCM0UwMDFFNUU3NzYzNjc=",
 "snippet": {
  "playlistId": "WLVZXy7bk3BRN0-p2URgcsrQ",
  "resourceId": {
   "kind": "youtube#video",
   "videoId": "0gYgzN6B0y4"
  }
 }
}

I get:

404 null

- Show headers -

{
 "error": {
  "errors": [
   {
    "domain": "youtube.playlistItem",
    "reason": "playlistItemNotFound",
    "message": "Playlist item not found."
   }
  ],
  "code": 404,
  "message": "Playlist item not found."
 }

}

Down for just me?
Have Google blocked updates for the Watch Later playlist?
Is the service broken?

Looks like the "bug" was just part of the transition period where YouTube planned to remove the ability to fetch the Watch Later and Watch History playlist through there API. As Tym commented the "bug" is/was tracked here: https://code.google.com/p/gdata-issues/issues/detail?id=8145 .

TLDR:

"Requests to retrieve playlist details (playlists.list) for a channel's watch history or watch later playlist will return an empty list after September 12, 2016. Requests to retrieve playlist items (playlistItems.list) in either of those playlists will also return an empty list after that time. This is true for the new values, HL and WL, as well as for any watch history or watch later playlist IDs that your API Client may have already stored."

https://developers.google.com/youtube/v3/revision_history#september-15-2016