Some songs not syncing on iPod Touch
I have a 2 year old iPod Touch, and it has started playing up. The other day, I plugged it in to sync some new music, and it erased and re-added my music. Takes hours, as I have thousands of songs. I then realised that it had missed quite a few songs in the sync, and each time I connect my iPod, it still misses them. When connected in iTunes, I go to the left side and where it says "On My Device", and "Music", it shows the songs on the iPod. I then find some songs greyed out, with a dotted circle on the left. I have attached a photo showing this.
There is plenty of space on the iPod, and the songs are in my iTunes library and play fine. I don't use the cloud, and the songs are mostly ripped from CD's as I very rarely use the iTunes store. Any ideas? It is really frustrating to listen to an album and find songs missing.
iPod, iOS 15