Custom songs and playlist issue

I have songs I put on my iPhone that are not in the Apple Music library because they are custom songs I make on my own for fun. I started to notice this problem about 3 days ago. Maybe it’s been happening for a week maybe. I use to never have this issue because I have a playlist with currently 40 songs on it with custom songs. Now when I go to add a custom song to a playlist one of two things happens. 1: I see that it was added to the playlist and a second or two later they disappear from the playlist. 2: I see the songs I added to the playlist and when I try to add more songs when I add more songs they songs I added just disappear. I have no problem with Apple Music I get from the library. Now here’s the kicker, I thought it was the new update so I updated to iOS 18.7 and the problem still happens but this time one song stuck in the playlist. Now I told you before I use to not have this problem so I do have different playlist with custom songs in them. But I added I think like 14 songs and 1 stuck on the playlist and the others just vanished after trying to add more music. What to do? Any advice?