After a while synced songs become unplayable

[RujinXERO]

After a certain period of time I have to re sync an entire playlist because some synced songs become unplayable. if i try to play them it says they arent synced. connecting to the same wifi and having both spotify apps open does not sync the unsynced songs. i have to turn Available Offline on and off and sync the entire playlist again to get those songs back. this has happened to me on both Android and iOS.

during my brief time with an android phone i noticed this started happening and that it never happened on my iPhone before this. in fact i remember a time when songs i had synced through itunes would automatically show up as local files on my iphone. now that i'm back on iphone this no longer happens. everything works exactly as it did on Android where now after a period of time my synced songs become unplayable and yet on native music app those same songs are working just fine. so that leads me to believe my synced songs through iTunes arent being read by spotify anymore.

so i have two questions, am i delusional was this ever a thing, iTunes songs being considered local files on the Spotify iOS app?

and is there anyway i can stop these songs to become unsynced?