'YouTube API "playlistItems" does not return all items of the "Uploaded" playlist

I am wondering if anyone knows what could be the cause of this.

On a channel's upload playlist, it states there are 143 videos in the playlist:

When I use the "Playlistitems" API (with paging):

I get 138 items.

I have singled out a specific video that is in the Playlist on YouTube as an example. Video ID Q3UDhRDLbPg:

But when I use the "Playlistitems" API explorer, on the playlist and specify the specific video, I get zero results.

The video is public and was uploaded a few days ago. Some videos that were uploaded on the same day does exist in the results too.

Has anyone seen this problem before and might know the cause of it?

youtube-api

Solution 1:^[1]

This issue is solved.

As @stvar pointed out, there is some kind of a delay in YouTube's backend, some videos might take longer to be included than others.

All videos are accounted for now, 4 days after the upload time.

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Solution	Source
Solution 1	corgrath