Gutenberg: Preview don't work

[skiokko]

Describe the bug
The preview of posts and pages don't work, it show only the saved content not the preview one. The preview work only if I reload the preview page after 3-6 seconds.
Details here: https://youtu.be/FhCssW8JpEc

To Reproduce
Steps to reproduce the behavior:

1. Go to Pages
2. Edit or create a new page
3. Preview it
4. See error

• Device: desktop
• OS: W10 with XAMP PHP 5.6
• Browser Chrome
• Version latest

Additional context

• This issue happen sometime also with the original WP Themes like Tweenty Fifteen and without any external plugin.
• This issue don't happen with the latest WP Theme Tweenty nineteen.

[soup-bowl]

Reproducing this on the edition of Gutenberg built into WordPress 5.0. Can also confirm that reloading the preview shows up the preview, so not necessarily broken just not working as expected.

Device: Laptop.
OS: macOS Mojave
Browser: Chrome
Site Host: Ubuntu 16.04
Site Server: Apache
Site Theme: Custom fork of Sparkling (here).
Site Caching: None.

[designsimply]

Thank you for the video! I am closing this one as a duplicate of #12617 and would like to continue the conversation there.

[designsimply]

@skiokko would it be possible to get a list of your active plugins here on this issue even though it's closed? When we come back around to testing #12617 it would be cool to have that documented if possible.

[skiokko]

Hi,

I tested the issue also with no plugins activated and with the WP Theme Twenty Seventeen and I got the same issue. But this issue not happen always. It's really strange.

[designsimply]

It is strange! I can see that a few others have reported it, but I'm still having trouble figuring out steps to replicate the problem in testing.