What happens with music on TikTok?

Why does some songs become unavailable? I feel like it happened only today, it affected only the originals of the songs and not their re uploaded versions (for now I know only about chainsaw man reze arc ost and this song) videos still play audio but I can’t listen to them when I klick on them and also I can’t use them for the video, TikTok asks me to “create a similar one”. Is that a regional restriction or something like what happened with universal music group a yer ago?