Problem solved:
When uploading files or large (relatively) amounts of data to the server, you may encounter error 500.
At the same time, in the logs of the site and the web server, you will see something like:
mod_fcgid: HTTP request length 137536 (so far) exceeds MaxRequestLen (131072), referer
This is typical in cases when PHP is running on the server in FastCGI mode
To fix the error, open the configuration file of the module, which is located on the path:
/etc/apache2/mods-available/fcgid.conf for Debian, Ubuntu and OS based on them
/etc/httpd/conf.d/fcgid.conf for RHEL-like — CentOS, Fedora.
In it we find and make edits to the lines
FcgidConnectTimeout 60
(can be enlarged)
FcgidMaxRequestLen 33554432
MaxRequestLen 33554432
(these lines probably won’t be there at all, but they need to be corrected or added. By specifying this number, we will increase the size to 32 megabytes. )
After that, do not forget to restart the web server.
After that, everything began to work as it should
Thanks for solving your own issue.
I note that a properly configured server should respond with status 431 when the posted content is too large. A 500 is a common catch-all and doesn’t help the initial narrowing down of a problem.