Can you please share some screenshots and the code that creates the block, callback function? I've re-checked on my local site and see the callback result updates as well.
Click on the Edit and Preview button of the block, it reloads and fetches the new data as well. Screen record https://share.getcloudapp.com/X6ue60En. Can you please deactivate all plugins except Meta Box and MB extensions to re-check the issue?