pfSense

Using the firewall for that many certificates is an atypical use case for which it was not designed. From reading the thread it sounds like the device isn't handling the request fast enough, but the only way to fix that would be by increasing the script timeout/nginx timeout. The script timeout was set to its current value to keep certain processes from breaking things by running too long (or indefinitely) via PHP, so increasing the timeouts in the code is not likely to happen as it would negatively impact a wider portion of the user base.

If someone wants to create a separate feature request/PR to offer a GUI knob to adjust the timeouts, that is a more general solution that could help this case.