Hi @Christiaan,
I create a playlist with ONE song , synced it to serato successfully.
Then i deleted the song in LXC library and tried to sync back from Serato to LXC but it stucks just for this only song .
Is your library complete in Lexicon right now? You can try deleting the Music/_Serato_/database V2 file, then open Serato so it creates a new empty database, then Full Sync from Lexicon.
Could be the database file is somehow broken and recreating it will help