fix music file downlods from PC iTunes to iPhone 12

I've been having problems with file downloads not from PC via iTunes to iPhone(s) not all being successful.

I'm thinking of deleting all my music files on the iPhone and starting again from scratch. My PC has all the music I want in the playlists that I want.

My question then is: Would this fix my problem? Y/N?

If Yes, then how do I go about doing this?

If anyone thinks there might be another solution, please express your suggestion. My mind is open to all suggestions

Thanks in advance