while I've constantly had problems in the past with standard TM automated backups to my Synology NAS, I did switch to TM backups using
TimeMachineEditor and whilst I loose the per hour snapshots (I prefer per 24hour @ 3am) I do get reliable backups I can restore with "Migration Assistant" to a replacement device. But then most of the files I generate/augment daily are on the Synology NAS or iCloud/OneDrive anyway so outside of the TM backup set I scope.
I Frequently had dropped connectivity (and plain acceptance of being not relevant) with TM, with my Macs and their Synology hosted backup files in the past, but since using
TimeMachineEditor to schedule the backup once per day and remove the hourly stuff, it's never failed me.