Mixed up album art in Music on iPhone 11 after iOS 14

Moved from iPhone XR to 11, after which my organised music library album art is all mixed up. The source folder & iTunes itself on my Windows 10 are still okay. All devices are up to date. Deleting all music and offloading Music app from iPhone (General-iPhone storage-Music), then re-installing music app before Re-syncing via iTunes made no difference, can you assist?