I have never once had Nextcloud updates work properly. It doesn't matter if I update as soon as the new version is ready or if I wait long enough for my current version to go EoL, the updater breaks something critical and my instance is non-functional.
Despite that, nextcloud/owncloud do what I want/need and I'm not sure if Syncthing does. So I keep stubbornly re-trying and just spin up a new instance when the old one dies.