Looking for experienced advice, should I be worried about missing scales?
 

Hello everyone, I come here looking for help!

My snake since his previous shed has been losing scales on his back and with every shed it seems to get a little bit worse.

He's a 3.5year old MBK living on a strict diet of frozen thawed mice, kept at a steady 20-25C enclosure with dry aspen shavings as bedding.

Do I need to worry about something specific or does this seem like just a scratch?