Time Machine does not recognize its own sparsbundle and starts a new one

Hi everyone, I have a regularly updated backup created with Time Machine on a Synology DS 923+ NAS connected via local network, which has worked perfectly for over a year. Suddenly, for the past few days, Time Machine seems to no longer recognize the sparsebundle file and is creating a new one, effectively starting a new backup from scratch in the same location.

Just to clarify, if the previous backup was named MyMac.sparsebundle, Time Machine is now creating a new one called MyMac-1.sparsebundle exactly in the same location.

I tried manually mounting the previous MyMac.sparsebundle as if it were an external drive, and it appears to have no issues. A disk utility check came back positive, and if I access the sparsebundle through Finder, I can see all the files and folders inside and even manually restore files from the backup. Despite this, Time Machine refuses to reconnect to it and starts the new backup instead.

Any suggestions? I’m using an MBP M3 Pro 2013 with Sequoia 15.1. Could the issue be related to the latest Sequoia update released a few days ago?

Carlo