Youtube API, PlaylistItems: list, maxResults - it works incorrectly

I have a specific playlist that contains 562 videos.

My goal is to get all the IDs of each video and put them on the List (Java).

I am using PlaylistItems: list and setMaxResults (50L) - the highest possible. Yes, in the end it returns me my 562 videos, but if I try to create a HashMap (no duplicates, each value is unique) based on the video id, it turns out that out of 562 videos, about 50 are duplicates.

I still cannot identify the pattern, if you do setMaxResults (49L) - then the number of takes will decrease by 1. If you do setMaxResults (48L) - then the number of takes will grow ...There is no setting setMaxResults (), the default is 5 - out of 562 videos with unique IDs, only ~ 340 will return at all ...

We get all the videos of the playlist

    List<PlaylistItem> playlistItemList = new ArrayList();    try {        String pageToken = "";        while (pageToken != null) {            logger.info("pageToken: " + pageToken);            YouTube.PlaylistItems.List youtubePlaylistItemsList = youtube.playlistItems().list("snippet");            youtubePlaylistItemsList.setPlaylistId("UUlatNLsHQYQ00TCT3Nfse6w");            youtubePlaylistItemsList.setMaxResults(50L);            youtubePlaylistItemsList.setPageToken(pageToken);            PlaylistItemListResponse playlistItemListResponse = youtubePlaylistItemsList.execute();            playlistItemList.addAll(playlistItemListResponse.getItems());            pageToken = playlistItemListResponse.getNextPageToken();        }    } catch (IOException e) {        logger.error("Error: ", e);    }

playlistItemList.size() = 562.

Now let's select the number of unique video IDs

HashMap<String, String> realVideoIds = new HashMap<String, String>();    try {        youtubeVideosList = youtube.videos().list("id,statistics,snippet");        for (int i = 0; i < playlistItemList.size(); i++) {            if (realVideoIds.containsKey(playlistItemList.get(i).getSnippet().getResourceId().getVideoId())) {                logger.info("getContentDetails: " + playlistItemList.get(i).getSnippet().getResourceId().getVideoId());            }            realVideoIds.put(playlistItemList.get(i).getSnippet().getResourceId().getVideoId().trim(), playlistItemList.get(i).getSnippet().getTitle());        }        logger.info("realVideoIds size: " + realVideoIds.size());

realVideoIds.size() = 512.

Total 562 != 512. As I wrote above, the smaller the MaxResults value, the greater the difference.

Thank you for your attention, I will be glad for any help =)