I also noticed My Shazam Playlist was not completely synced to Spotify. I exported a CSV of all of Shazam songs on my browser (it is quite involved). I tried to import all my Shazam songs via a that CSV using Soundiiz. It imported 66 out 77 as it could not find the other 11 automatically. The song tittles or artists were quite difficult with symbols, featuring and remixes. I had to manually search those 11 not found and add them myself.
TLDR: Spotify will not always find the same title, artist as it is shown in Shazam and will not import the song if it can not ensure it is the correct one.
Same issue here. Shazam/ Spotify worked harmoniously for years but it seems like there's certain songs I'm unable to get from Spotify to a Shazam playlist, manually or automatically. I've reached out to Spotify and they suggested contacting Shazam since everything looks good on their end.