Navigation Menu in left panel of Site Editor takes minutes to load and when done Navigation block on canvas gets replaced with error placeholder

[porg]

Reproduction

1. Visit a page in the frontend. In a role which has the Admin Menu.
2. In the admin menu click "Edit Site"
   • Note: I use a plugin which only shows the admin menu on hover. Unrelated to reported issue. Mentioned for completeness.
3. My header template part is composed of these blocks:
   • Group with ☑︎ Inner blocks use content width
     • Row with justification set to Space between items
       • Site Logo
       • Navigation
         • Note: Menu was converted from a classic menu earlier.
         • Has ca. 40 items in total.
         • Maximum depth: 4 levels: Visible root level → Sub-menu → Sub-menu → Deepest menu item.

• ✅ All done loading ca 3-4secs after entering Site Editor.

4. In the Site Editors black left menu pane it shows "← Home ✏️ " — Back button (left arrow icon), name of the page exemplarily shown in the template editor, edit button (pencil icon)"
   • This is not yet present in WP 6.1 and will be included in WP 6.2 in only about 2 weeks.
   • ❗️ Hence my bug report as a serious warning, that something here is not in order.
5. Click on the "Navigate up" button.
   • This loads the hierarchy of your menu, which can be used to interactively restructure/rename your menu.
   • ❌ But loading this takes 1-2 minutes (!) despite being only ca 40 items total.
   • The moment it is done loading the navigation menu in the Site Editor's left panel the rendered navigation block disappears from the canvas and instead shows an error placeholder This block has encountered an error and cannot be previewed.
   • Opening Safari > DevTools > Console shows:

Error: Minified React error # 185

[Error] Error: Minified React error #185; visit https://reactjs.org/docs/error-decoder.html?invariant=185 for the full message or use the non-minified dev environment for full errors and additional helpful warnings. — react-dom.min.js:1:82575
	ar (react-dom.min.js:1:53537)
	(anonymous function) (react-dom.min.js:1:54005)
	tt (react-dom.min.js:1:38846)
	Jr (react-dom.min.js:1:80908)
	Zr (react-dom.min.js:1:80478)
	Gr (react-dom.min.js:1:80012)
	(anonymous function) (react-dom.min.js:1:91514)
	xl (react-dom.min.js:1:92025)
	fl (react-dom.min.js:1:85796)
	fl
	zn (react-dom.min.js:1:32462)
	(anonymous function) (react-dom.min.js:1:92022)
	xl (react-dom.min.js:1:92025)
	ol (react-dom.min.js:1:84540)
	ol
	v (react.min.js:1:3387)
	ce (react.min.js:1:5530)
	(anonymous function) (load-scripts.php:10:16079)
	P (load-scripts.php:10:15887)
	E (load-scripts.php:10:15944)	

Screenshots, screen recording, code snippet

• Screen Recording: 1m10s, with audio comment
• Note: Long wait time in left panel shortened in screen recording to ca 10secs, but in reality took ca 2min.

Navigation.Menu.in.Site.Editor.runs.into.timeout.mp4

Environment info

• Wordpress 6.1.1 with plugin Gutenberg 15.3.1
• Safari 16.3.1 on macOS 11.7.4 Big Sur

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

No

[Mamaduka]

cc, @getdave, @scruffian

[kathrynwp]

While I wasn't able to replicate the slow loading time for the Navigation sidebar, I did get the same This block has encountered an error and cannot be previewed. error:

Tested with:

WP 6.1.1
Gutenberg 15.3.1
Twenty Twenty-Three
No other plugins active

[Mamaduka]

I think a similar issue was fixed recently and should ship with Gutenberg 15.4 - #48668.

[jorgefilipecosta]

This issue is to the same as #48668 and was fixed in a PR by @scruffian #48219. So I expect it not to happen in 6.2 or Gutenberg anymore? Also, for awareness, I think the navigation item is not going yo ship with 6.2.

[porg]

Gutenberg 15.4.0 plugin:

• Seems fixed.
  • ✅ Loading the page hierarchy in the left sidebar took 8secs (better than 2mins!)
  • ✅ When that was completed, the navigation block on canvas remained
• Good that the navigation item is not included in 6.2 b/c it has other remaining issues too.

[porg]

@jorgefilipecosta The linked issue in your comment is this very same issue here. You must have mixed up issue numbers.

[Mamaduka]

Thanks for the confirmation, @porg! Closing the issue.

[jorgefilipecosta]

@jorgefilipecosta The linked issue in your comment is this very same issue here. You must have mixed up issue numbers.

Correct I pasted the wrong link I updated my comment 👍