I changed the WevDAV URL before reading the FAQ! I’d been using Dropbox and was changing to a Swiss Nextcloud server.
I have three Joplin devices - a Linux PC, an Android tablet and an Android phone. Trying to fix things only made them worse. Although I’ve stopped sync now, all three Joplin instances are different. The one in the Linux box is in the worst shape.
From the FAQ, “On your WebDAV service, copy all the Joplin files from the old location to the new one” is gibberish to this newbie. Is there any way I can compare and sync all three Joplin instances off line? I just don’t trust what’s left in the two clouds at present.