Describe the bug
In the widgets area, I do not get access to the Save button unless i duplicate a whole block and then edit that save everything and then go back and delete the original block.

Since the last gutenberg update even after duplicating the block and editing it, when i get the save button, it changes to Saving ... and in the bottom left i get a very quick error message saying "There was an error. object Object"

Having googled and checked here, i can confirm i get access to wp-json with no issue

and as soon as i deactivate Gutenburg plugin, go back to the block editor ... i paste the text in where i want it, hit save and all done.

To reproduce
Steps to reproduce the behavior:

1. Go to 'widgets'
2. Edit anything ...
3. No access to save button
4. Duplicate block to edit
5. Edit the duplicate block
6. Click save
7. Quickly check for error message in bottom left

Error message : "There was an error. object Object"

and the save button sticks on "Saving"

Expected behavior
Well i have been living with the having to duplicate edit, save, return, delete old copy, save again, check ...

But clearly i would prefer the save to work with out having to go through all of that. Just a working save button after i edit some thing would be better.

Screenshots
If applicable, add screenshots to help explain your problem.

Editor version (please complete the following information):

• WordPress version: 5.5.3–en_GB
• Does the website has Gutenberg plugin installed, or is it using the block editor that comes by default? gutenberg plugin
• If the Gutenberg plugin is installed, which version is it? Version 9.4.1

Desktop (please complete the following information):

• OS: windows 10 latest updates
• Browser chrome
• Version Version 86.0.4240.198 (Official Build) (64-bit)

Additional context
Hosted on 20i's wordpress cloud.
With jetpack installed

• To report a security issue, please visit the WordPress HackerOne program: https://hackerone.com/wordpress.