Not op but I have several Synology NASen using Btrfs volumes with no issues that I can recall in the past six years. I’ve replaced all of the drives twice to increase available storage and that’s it. The two I have at home are both set to autoupdate and do monthly disk scrubbing—they automatically email after scrubbing with any issues. They’re really pretty hands off devices overall.
Does your synology utilize BTRFS? If so, what is your experience with it? I'm currently using a FreeNAS box that runs on ZFS that has been very reliable for me over the years. I can't really see giving up the power/reliability of ZFS to move to a synology setup, but I like to keep tabs on BTRFS progress.