Pattern previews do not load reliably

[desrosj]

Description

I've noticed in my testing of 5.8 that pattern previews are not loading reliably. Sometimes, they do not load at all.

Step-by-step reproduction instructions

1. Open the Block Inserter.
2. Click patterns.
3. Observe patterns not loading correctly.

Sometimes, they do load, but fail after returning to blocks, and clicking patterns again. Other times you need to refresh the page after they load successfully to trigger the issue again.

This also happens when viewing pattern suggestions for a specific block.

Expected behavior

Block pattern previews should display.

Actual behavior

They do not.

Screenshots or screen recording (optional)

WordPress information

• WordPress version: 5.8 RC2
• Gutenberg version: Not installed
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? Yes

Device information

• Device: Macbook
• Operating system: MacOS 10.15.x
• Browser: Reproduced in Firefox nightly (91.0a1 (2021-07-07) (64-bit)) and Version 89.0.4389.128 (Official Build) (x86_64)

[desrosj]

Also just noticed that this happens when choosing a layout when inserting a Query Loop block.

[skorasaurus]

Hi,

Thanks for reporting;
This appears to be a duplicate of #29436 . Feel free to add your reaction and follow its progress in the issue. Please reopen and comment if this is different than that issue.