Getting 500 Server error

Hi, I seem to be having some sort of a server issue. I'm getting a 500 server error when trying to save a post. It does seem to save it, but every time it sends me to a blank page with the error. The one exception to this was the last time I tried and it gave me this error.

Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 1720320 bytes) in /home/admin/public_html/wp-content/plugins/wpmu-dev-seo/includes/external/simple_html_dom.php on line 1628

Additionally I use Elementor as my visual builder and when I try to save with it I also get the 500 error.

I have granted support access to allow the experts to take a look if needed.


  • Soumendra Mishra
    • Recruit

    Hello Shane,

    Hope you are doing well today.

    The “Allowed memory size of 268435456 bytes exhausted” mostly caused due to less memory allocation in the site. But as I can see the memory limit allocated to your site is “256M” which is mostly okay to run the site, but as the error showing that your site requires more memory than “256M”, can you please increase the memory limit to “512M” to get that working on the site?

    For increasing the memory limit you can refer the instruction in the below link:

    Also, as the site needs more memory which refers that one or more of your plugin(s) and/or theme needs more memory to run its functions.

    An essential step at this point is to run a full theme/plugin conflict test so please deactivate all the plugins and please try following steps:

    First of all please create a backup of your site in case you lose any settings during the test so that you can restore that to get to a previous working state.

    Then deactivate all plugins and MU-plugins apart from WPMUDEV Dashboard and Smart Crawl Pro.

    Activate the default theme like TwentySeventeen. clear all caches (including browser cache) and check again if the issue is still there. If not, it means that something is conflicting, so start activating the remaining plugins and theme, one by one checking each time to see if you get the reported issue, thus finding the conflicted combination.

    The following flowchart image can assist you during this test:

    If this is a live website with traffic, I’d rather advise to create a staging environment, meaning a complete and exact copy of this installation into another location/folder in the same server, using a separate database, and perform the test in there instead without worrying about the live site.

    Please try that and let me know about the result and I’ll investigate it further.



  • Shane
    • Recruit

    Hi Soumendra and thank you for the response. I managed to fix the issue. I updated the memory..that did not fix it. I then decided to test some plugins on the live site that would not effect the front end, humming bird etc… It appears that ‘Query Monitor’ was the culprit because when I deactivated it the issue resolved. I have considered creating a staging site in general and guess I should go ahead and do so now for future issues…as there always are :slight_smile:

    With a multisite is the process pretty straight forward to clone it…in the past I’ve always used backup buddy to migrate sites..Is WPMU Snapshot a pretty good source to accomplish this task?

    Thanks again!

  • Kasia Swiderska
    • Support nomad

    Hello Shane,

    Is WPMU Snapshot a pretty good source to accomplish this task?

    Sadly, but no. Snapshot is a backup tool, it was designed only for that – not for migration. It is possible to migrate a site with Snapshot, but we don’t really recommend it (it might or it might not work).

    But we are preparing new plugin Shipper that was designed only for migrations. If you want you can take a look on beta here

    kind regards,


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