Sorry being rude.
I had a lot of work and trouble with “your” Gutenberg (experience). Maybe it’s good for new installations but definitly not testet with existing ones.
Like I said above: Try to copy an existing code to the new editor and see what happens…
Not even worth to be called a “Beta”.
Always the same reply? Sorry but there are too many bugs to report them 😉 Please just test Gutenberg on existing WordPress Installations and you’ll see that it does not work at all.