There was an attempt to fix this issue at
Maybe the fix was not enough. Are you sure 1.20.2 is not working? Are you talking about Android or Desktop by the way? The string fetch_new_messages: ignoring uid does not exist in the latest versions. For Desktop, try updating to the next release: 🧪 Help testing the upcoming 1.20.X release
One fix you can do on the server is to reset UID validity for inbox, causing redownloading of all messages. Delta Chat will ignore duplicate messages based on Message-ID header anyway.