Some iTunes tracks will not sync or play reliably on my iPhone 6s.

Since upgrading my iPhone 6s to iOS 11.1 I have had problems with ITunes /Music. I have updated to iOS 11.1.1 and the latest iTunes for windows.

Some tracks will not sync reliably. I get some tracks from the album but error message "Unable to convert file" for others. They are all mp3 files from Vinyl Studio. The next time I resync I get a different set of tracks with errors for new ones not uploaded.

Of the tracks that do upload, some grey out and will not play while others look fine but play for less that 1 second before stopping.

These tracks all play fine on the PC in iTunes and on my 10 year old iPOD classic.

Any ideas?

PJ