Preview error: The preview could not load due to the iframe response being incomplete. This is most often related to a plugin conflict, or customizations introducing a PHP error

[100leiden]

Hi I’m getting this error whenever I try to edit a layout builder and choose custom post type product as preview page.

It does work when I choose the frontpage or if the page is empty. As soon as i add a section I get the error when product is set as the preview.

Already tried debugging theme, plugins etc.

See private note for details

[tristup]

Hi @100leiden,

Thanks for reaching out.
I have checked your website and found the issue you described here. There might be some different reasons behind your issue, I would like to suggest troubleshooting the following common issue to help us to recognize the reason.

1.Theme Related Issue
2.Plugin Conflict
3.Theme Update related issue
4.Child Theme Related issue
5.CSS/JS Customization
6.Disabling Cache
7.Disabling CDN

If you discover that an issue is coming from a custom code or 3rd party plugin, kindly consult with a developer or contact the plugin author. Please note that we do not provide support for custom codes and 3rd party plugins.
If none of the above helps and you are still getting the issue, please copy your live site to a staging server so we could troubleshoot freely without breaking your live site.
And give us access to the secure note including:

– WordPress Site URL & Login URL
– WordPress Admin username/password

To create a secure note, click the key icon underneath any of your posts.

Thanks

[100leiden]

Alright, just checked off the list:

1. Checked
2. Checked (CPTs (Custom Post Types) are registered through plugin that also generates code if you want to disable that plugin, but that doesn’t fix the error. We now register the CPTs with custom code in functions.php)
3. Checked
4. Checked
5. Checked
6. Checked
7. Checked

Issue doesn’t seem to be resolved after checking all these items. Can you please login on the site, see secure note from first message, and find the issue that’s causing this?

I just found these 2 errors in the console: VM2350:1 POST https://***.nl/product/concrete-anchoring-repair-car/ 500
app.6f62d0f.js:2 Frame missing CORNERSTONE_FRAME signature. This could mean WordPress did not shutdown properly or this URL could be cached even though Cache Control headers are present.

Also whenever you create a new layout and select product as preview then it works until you add a section to the layout. Then the following errors show up:

app.6f62d0f.js:2 POST https://***.nl/product/concrete-anchoring-repair-car/?cs-render=1 500
app.6f62d0f.js:2 Failed render SyntaxError: Unexpected token E in JSON at position 0

Thanks in advance!

[prakash_s]

Hello @100leiden,

Thanks for sharing the login details it seems that it is an issue of cache, I went ahead and purge all the cache from the SiteGround Optimizer plugin. I would suggest you please purge all the cache and then temporarily deactivate the plugin SiteGround Optimizer and SiteGround Security, I would also suggest you please clear your browser cache and then check it again. I have checked a few of your layouts and it is working fine at my end.

Thanks