Update button remains disabled when update failed

[ktmn]

Describe the bug
I updated some plugins in another tab and during that I saved my gutenberg post. Since plugin updates put the site in "Maintenance mode" the post update failed, console showing:

Failed to load resource: the server responded with a status of 503 (Service Unavailable)

Which is understandable, how ever the "Update" button remains disabled even after the maintenance is complete.

This prevents from trying to save the post again, forcing to refresh the page and lose all updated content.

To Reproduce
Steps to reproduce the behavior:

1. Update or install some plugins in another tab
2. Try to save a post
3. Maintenance mode over
4. Can't attempt to save again

[nfmohit]

I do not seem to be able to reproduce the issue. Here's a screencast from my end:

Do you think I'm missing something here?

[ktmn]

I tried with Twenty Seventeen and it also worked like your screencast.

The previous theme I used had metaboxes. So to test I installed a random plugin that also adds a metabox and that reproduced my issue.

Along with this error:
POST .../wp-json/wp/v2/posts/117 503 (Service Unavailable)

I also get this:
POST .../wp-admin/post.php?post=117&action=edit&classic-editor=1&meta_box=1 503 (Service Unavailable)

So looks like the presence of metaboxes could be the culprit.

[lubimow]

@mtias I have the same problem in plugin version 3.4.0

[blogxkomo]

i have same problem too

[noisysocks]

I was able to reproduce this by:

1. Configuring my dev environment to use a local WordPress installation by setting "core": "~/path/to/wordpress-develop/build" in .wp-env.json

2. Activating the 'Gutenberg Test Plugin, Meta Box' plugin

3. Creating a post in the block editor and entering some content

4. Forcing maintenance mode by creating a file at ~/path/to/wordpress-develop/build/.maintenance which contains.

   <?php
   $upgrading = time();

5. Returning to the editor and clicking Save draft

6. Deleting ~/path/to/wordpress-develop/build/.maintenance

Although the site is now not in maintenance mode, you cannot click Save draft again.

I confirmed that this only happens when there is a meta box enabled.

[noisysocks]

Possibly related: #19780

[paaljoachim]

Is this issue still valid?

[paaljoachim]

Robert @noisysocks Can you recheck this issue? Thanks.