Tracks randomly not showing

I’m using a 32 gb sd card with all my songs on there and none on internal memory. Just updated to 1.39 firmware. I’ve had a persistent and long running problem where a small amount of songs which are on my SD card, and I can access and play via my pc when connected, just do not show on the player itself, not as a track pops up in random play, or when searching through the folder on the player itself. Is this something that has a solution or someone has seen this before? As far as I can tell it only affects 2 tracks which I wanted to specifically play. It may affect more but I wouldn’t know unless I had a specific song in mind that I wanted to search for.