I ran into this same problem (watch is an s3, phone is a Note 9). I started receiving these notifications, and it would say "6 Tracks Received..." So I did some rooting around on my phone, and I figured out that the "tracks" it was trying to sync up were random audio files that I just needed to clear out. I just removed the tracks, and haven't gotten notifications in the last hour (notifications were coming roughly once every 2 minutes).
To see what tracks your watch is trying to pull off your phone, open the My Files app on your phone, and under Categories select Audio. When you open the Audio folder, the folder that I found these random tracks under was called "Downloads" (I think: I don't remember for sure because I didn't think deleting files on the phone would work). The file names were random number and letter combinations -not anything coherent- so I knew they weren't anything that I had intentionally downloaded. Once I deleted them, the notifications stopped. Basically, you want to look for a folder under the Audio section that has the same number of files in it as the number of "tracks" you supposedly received on your phone. Once they're gone, the notifications will stop.
I hope this helps!
Tried changing the app permission and storage setting. And this is still a problem!!! Every 5 seconds I get a "6 new tracks added" notification. This stupid watch vibrates all damned day now!!!