Symptoms
When uploading an image in WordPress, the below error was received shortly after reaching 100% upload.
"Post-processing of the image likely failed because the server is busy
or does not have enough resources."
Description
WordPress can try using the PHP Imagick extension if it is enabled to upload images. Sometimes this process can use a lot of memory in the webserver. Triggering the memory limits will cause this message to appear. When the LiteSpeed Web server is in use, a 503 error will appear in the browser console.
Workaround
If the LiteSpeed Web server is in use, try increasing the PHP limits in the LiteSpeed console. See the below URL for more details.
LiteSpeed 503 process memory troubleshooting
If the LiteSpeed Web server is not in use, try increasing the PHP memory limits via MultiPHP Manager for the account.
For Global settings, use WHM MultiPHPini Editor:
For cPanel individual account settings, use cPanel MultiPHPini Editor:
Alternatively, disabling PHP Imagick from the WHM Module installer interface would also resolve this problem. Disabling the module could have some harmful effects on functions in PHP that require it. So if you are using PHP Imagick, this should be taken into consideration before removing it.