Thank you for reaching out to the Community and welcome.
As mentioned by @kaworu_bloodpaw, this issue could be related to the Autoplay function. However, there's a couple of things more that may affect your playback as well.
After checking the Autoplay function, we'd recommend checking if the Enhance button located on the top of the playlist is turned on as this feature adds some similar songs to the playlist you're listening to. If so, turn it off and try again.
Also, it's worth checking if you have some songs added by mistake to the Play queue. If so, you can clear it by following the steps mentioned in this article.
Hope this helps. We'll be on the lookout.
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