Personally, I'd have set up a volume on the Synology and used it for time machine and not bothered with CCC. It's good for disk images, but I wouldn't depend on it for anything else.
I've had Synology NAS's for years, I still rate them for stability and performance at a good price.
Time Machine backups on NAS shares get corrupted and have to be rebuilt after a few weeks. Apple S/W doesn't seem to be able to deal with NAS shares - unless there's been a major overhaul of NAS and Apple S/W recently. Seems to happen on all vendor NAS units.
I've had the same experience as you but with ReadyNAS units over 6+ years. Stable and reliable with very good performance.