thats a core block, its not something the Theme has any control over.
But this is the second topic where something in the editor is not working as it should.
Can you check for plugin conflicts ?
You may also want to try increasing your PHP Memory limit on the server.
No idea. I just recreated the menu and it works. The css is not looking good but I will solve that. For a couple more issues I am suspecting WPML has some bugs or conflicts. One of them was confirmed with WPML so as to solve in the near future.
also some issues seem not to happen anymore after I removed the generateblocks alpha and replaced it with the working version. It is bad though, as I cannot have the custom post views I liked with generateblocks.