I used the Owncloud client a long time for synchronisation. If it has been lost the connection to the server (e.g. WLAN), it immediately started to resynchronize if the connection was reestablished. I was very surprised and disappointed that the official Nextcloud client does not have this behaviour, it stays disconnected until I manually force the synchronisation.
Maybe I have overlooked a configuration option, but for now I would call it a bug.
I am using the current MacOS version.