Classic Edit vs Advanced Layout Editor

Hi everyone.
I’m having trouble switching between editor types.
1) I create a post, insert three text blocks, and save as a draft.

2) I click “Advanced Layout Editor” and everything seems fine.

3) I click “Default Editor” and the three text blocks become a single shortcode.

4) I add two more text blocks and save.

5) I click “Advanced Layout Editor,” and then click “Default Editor.” The added text blocks have disappeared.

What am I doing wrong? Why is this happening?
I’ve entered the login details in the private field.
Thank you for your cooperation.