Quick summary

When the Table of Contents block is nested inside a column, it's throwing an unexpected error in the editor: This block contains unexpected or invalid content.

This stops the block from updating to match the page.

Steps to reproduce

1. On a new page or post, add the Table of Contents block, along with a couple Heading blocks to give the TOC block something to reference.
2. Publish the page and refresh.
3. Next, add a columns block, and place the TOC block inside the Columns block.
4. Update the page, and refresh once more.

What you expected to happen

The block to not break when nested.

What actually happened

The block displays the unexpected error. Selecting Attempt Block Recovery fixes, but the issue returns the next time you load the editor.

Example

⚠️ Impact - If the user does not select Attempt Block Recovery, the TOC block will not update to reflect new changes on the page.

Selecting ... and Resolve Shows:

From there, selecting Convert to Blocks changes the Table of Contents into a Static list, which no longer automatically updates, so it's feasible that users will end up breaking their TOC's automatic workings while trying to resolve this issue.

Context

Came up while helping this user create a page with a 2-column layout and Table of Contents blocks in their right-hand sidebar: 38414229-hc

Platform (Simple, Atomic, or both?)

Simple

Theme-specific issue?

Not Theme-Specific.

Tested on Simple, using multiple themes: Twenty Twenty, Penscratch 2

Browser, operating system and other notes

No response

Reproducibility

Consistent

Severity

Some (< 50%)

Available workarounds?

No but the platform is still usable

Workaround details

There's no alternative way to add the TOC block to a column and prevent that error from appearing. The user will need to select Attempt Block Recovery every time they update their page.