Nextcloud "overwrite.cli.url" was changed to internel IP ? VPN?

Hello

Nextcloud 21 on Debian Server

I changed some settings when connected over VPN in the Nextcloud backend, I think only email settings…
Later, without VPN, I could not access Apps anymore.
I detected “overwrite.cli.url” was changed, so I changed it to “”
Then I worked in Nextcloud backend again. Changed eMail settings.
Now, “overwrite.cli.url” was automatically changed to publick URL

So I am wondering, maybe this can causes some problems? Using Nextcloud Backend (admin settings) sometimes with and sometiimes without VPN ?

Thanks