This definitely this. TiN coating is not stable for long term. I’ve had one fail inside me and what you’re describing happened. Get it removed
BONUS PICS: xNT after removal. The glass looked a bit murkier, but otherwise in good shape: [xNT_zoom] I also removed my old magnet during this visit (see my wrapped finger in the above pictures?). It was in for 10 months. [TiN_Magnet]