Changes the sub-block of block are not saved

Steps to Reproduce

• log in as an admin
• create a page with layout builder
• Open LB and add block with sublocks
• Fill in the fields of the block, add at least one sub-block > save the block and the layout
• check the block
• click on the Layout button
• edit the block
• edit fields
• click on the Update button
• click on the Update block button
• save the layout
• check the sub-block