So I have downloaded Wappler v6.4.2 and installed it then opened the original part completed project which gave me the errors.
And now everything works as expected, no errors and the project settings save when the "save" button is clicked.
I still have an issue with the rogue db database but that is unrelated as I caused that problem early in development so by changing the project settings to not include a database those issues have also gone away (which I couldn't do in the most recent version since the project settings would not save/update).
At some point in development I had created a second database (I think I know where) then changed my mind later but didn't notice after reverting to using default database that I had two listed.
So I added the default database back (using the properties panel which now works), deleted the second database, restored the migrations (from a backup I made whilst trying to fix all this) then lastly a quick find and replace on the api files to replace "database" (the imaginatively named second database) with "db" the default database created when using the properties panel and voila, default "db" in place, tables and fields put back using the changes/migrations and I am back.
Created a new target "staging" on Hetzner cloud, deploy and that also works now.
