I recently updated a wordpress multisite to 5.6 and since that update, new uploads to the media library don't add new entries in the mysql database, and consequently don't show up in the media library. I have confirmed that normal posts successfully write to the database and that media library uploads successfully put the file on our server.

The error I see when uploading a new image is, "post-processing of the image failed likely because the server is busy or does not have enough resources. . ."

I'm testing with a tiny .png, just 8KB and 303x25 pixels

php settings: post_max_size 16M, max_upload_filesize 16M, memory_limit 512M, max_execution_time 300

While WordPress is attempting to upload the image, cgi/fastcgi maxes out the CPU. There are no php errors added to the debug log when the upload fails.

I've tried disabling all plugins and changing the theme to twenty twenty and twenty twenty-one.

So, I'm officially out of ideas on ways to fix this issue and am wondering if anyone else has ideas/has encountered this before.

Thanks!