502 Bad Gateway for BackEnd edit post

it’s very strange!
When I turn on debug mode – I can edit post or page with command:

define(‘WP_DEBUG’, true);

When I set define(‘WP_DEBUG’, false); post is not editable in Backend.

P.S. I’ve got 2nd site with the same template on the same server

I can edit post and page for 2nd site with enabled NextGen plugin.

Bug ticket was created – #336468

I’ve disabled all main plugins – NextGen with active status doesn’t edit post and page.
I’m ready to show a video screenshot on request.
Please refer to ticket #336468

I tried to flashDNS, Clear site cache, browser cache, changed browser type.

Hello @kibiribi,

Thank you so much for sharing.
Nevertheless, please, do not create a bug report directly to the inbox.
We first check any issue here, and then we can refer you to a bug report in case it’s necessary.

Ok, according to the information you provided, you mentioned that it’s visible on one site and not the other one. But that both sites share the same environment, correct?

Are those sites sharing the same plugins?
I know it sounds a bit far-fetched, but sometimes these issues are conflicts between more than one plugin.

So please, we do advise you to check first for conflicts if you are able to do so.
You currently have about 35 active plugins and two of them are cache related.

If the problem persists, you probably need to check for conflicts.
– Temporarily deactivate all your plugins except NextGen Gallery.
– Is the problem solved? Then, it was caused by one of your plugins. Please check one by one and find the one causing the problem.
– If the problem is not solved with the deactivation of the plugins, try changing to a standard WordPress theme, it could be a conflict with your current theme.

A full website backup is recommended.
Please keep us posted, we are happy to help!

ok. I will do and let you know the result.

According to your recommendations – I’ve deactivated ALL plugins (and template and cache and more).

The source of a problem that 2 plugins can’t work together
NextGen Version 3.3.17
and
WPBakery Visual Composer Version 4.12.1

WPBakery Visual Composer Version can edit post and page without active NextGen.
When NextGen was activated and WPBakery Visual Composer Version is active – post \page is not edited.

I recorded video and ready to provide it if you need. please contact me via my email.

Any workaround about this ?
I’m ready to provide my video of test.

Hello @kibiribi,

Thank you so much for following the troubleshooting steps.
This is really important because is one of the first questions we asked while creating a bug report.

Please, if you have some time, we′d like to take a closer look. If so, please send us a bug report here: https://www.imagely.com/report-bug, refer back to this forum thread and let them know Gaby referred you.

Do not forget to add the link to this forum thread.

Many Thanks.

Report bug was created…
done.

After manual Plugin update
from WPBakery Visual Composer Version 4.12.1? ===>?WPBakery Page Builder Version 6.2.0 problem was disappeared.
Page edit works well.

The problem was that Visual Composer was very old.
The case is closed.
Thanks for the support!
NextGEN don’t block page edit.