Same playlist appears differently

[LeNanner]

Hello everyone!

I have since the dawn of time worked on my playlist (currently 800+ songs) on my Spotify Free account. A while back, maybe a year or so, I got Spotify Premium on a new account. Because I hade such a large playlist I did not want to delete it so I just follow my playlist from my new account. This has worked really well up until last week. I made some changes to my playlist from my old account and all of a sudden some songs disappeared from my playlist, but only when looking at it from my new, premium account. Everything is fine on my original playlist on my original account but looking at it from my new account there are several songs missing and also some songs I deleted has come back and now I have doublets on some songs. Once again, everything is alright when I'm logged in on my original account but not when I use my new, premium account. Why did this happened and how can it be solved?

(I know now that you can just upgrade your account but I didn't know it back then, hence the double account solution)