Simple sites: Spacer Block shows editor error on all WordPress default themes 2011 - 2020

[inaikem]

Quick summary

Adding or editing a Spacer Block on a Post or Page with any default WordPress theme from Twenty Eleven to Twenty Twenty installed and active throws the following error:

This block has encountered an error and cannot be previewed.

The block appears as normal when viewed via public links, shows no recovery options in the editor (per the screenshot below) and its height can be adjusted via the editor's code view.

Screenshot:

Steps to reproduce

1. Open a Simple site.
2. Ensure any default WordPress theme from Twenty Eleven to Twenty Twenty is installed and active,
3. Open a new or existing Page or Post.
4. Add/edit a Spacer Block.

What you expected to happen

I expect the Spacer Block to be visually editable.

What actually happened

The block crashed but did not permit recovery. It can still be edited via the code view and is reflected as normal via public post/page links.

Context

4674003-zen

Simple, Atomic or both?

Simple

Theme-specific issue?

• Twenty Eleven
• Twenty Twelve
• Twenty Thirteen
• Twenty Fourteen
• Twenty Fifteen
• Twenty Sixteen
• Twenty Seventeen
• Twenty Nineteen
• Twenty Twenty

Browser, operating system and other notes

No response

Reproducibility

Consistent

Severity

Some (< 50%)

Available workarounds?

No but the platform is still usable

Workaround details

No response

[inaikem]

Closing in favour of #59846.