I had double clicked on the name of the first column of each table and pressed enter. This used to work.
I tried again. Now I had to double click, change the name, double click again and change the name back to what it was (after a mildly annoying wait of 2-3 seconds). I guess the new improvements on the UI don’t really update if nothing has changed.
I also experienced this today randomly on an app that has been stable, calling anvil.tables.get_connection_str() caused an internal server error. I had to go into each table in my app, rename a column, rename it back, and then after doing it for each table, the problem was resolved.