What version of mono are you using?
Installed Packages
mono-complete.x86_64 6.8.0-8.fc33 @updates
mono-core.x86_64 6.8.0-8.fc33 @updates
mono-data.x86_64 6.8.0-8.fc33 @updates
mono-data-oracle.x86_64 6.8.0-8.fc33 @updates
mono-data-sqlite.x86_64 6.8.0-8.fc33 @updates
mono-devel.x86_64 6.8.0-8.fc33 @updates
mono-extras.x86_64 6.8.0-8.fc33 @updates
mono-locale-extras.x86_64 6.8.0-8.fc33 @updates
mono-mvc.x86_64 6.8.0-8.fc33 @updates
mono-reactive.x86_64 6.8.0-8.fc33 @updates
mono-wcf.x86_64 6.8.0-8.fc33 @updates
mono-web.x86_64 6.8.0-8.fc33 @updates
mono-winforms.x86_64 6.8.0-8.fc33 @updates
mono-winfx.x86_64 6.8.0-8.fc33 @updates
monodoc.x86_64 6.8.0-8.fc33 @updates
These are the current versions for Fedora 33 (dnf does not show any available updates).
Also, how large are your job sqlite databases?
System 1:
ls -lu --full-time *.sqlite
-rw-------. 1 root root 233472 2021-07-29 10:20:00.149070786 -0400 Duplicati-server.sqlite
-rw-------. 1 root root 18098118656 2021-07-29 02:34:19.850664721 -0400 MYFGVUULA.sqlite
System 2:
ls -lu --full-time *.sqlite
-rw-------. 1 root root 233472 2021-07-29 10:20:00.149070786 -0400 Duplicati-server.sqlite
-rw-------. 1 root root 18098118656 2021-07-29 02:34:19.850664721 -0400 MYFGVUULA.sqlite
On the off chance that it is relevant, in the past I had to move the Duplicati directory to a different filesystem, and replaced /root/.config/Duplicati with a symlink. Systems have been running with this configuration for several weeks. Also, due to issues with disk space doing a rebuild, I have TMPDIR set in /usr/bin/duplicati-server to point to a temp direcotry on a filesystem that has more space - this is a more recent change.