my suggestion is to provide disk full alarms.
I am running duplicati in a synology environment. As it installs to /root/.config/Duplicati it quickly consumes all space on the root partition (approx. 600 MB free in my installation). It was only when the logs indicated that the disk went full, that I researched into this matter.
My workaround is to move the sqlite-Databases onto /volume1 and set a symlink.