Recently I started having the following problem in the domains of my server with WHM:
When running an asynchronous AJAX call in the background, I can not continue, that is, I can not access anything in the same domain by the same terminal that ran the call while the process does not complete.
This gives the impression of slowness in the system, when in fact it is only the problem of the domain being "locked" while there is a process in the background (even if you open another browser tab)
If you access from another terminal - even if it is on the same network - it accesses normally.
This is something that happens in local tests (using PHP Built in) because BuiltIn does not allow more than one simultaneous connection.
But this should not happen on the server.
As it was not like this before, I believe this is due to some change in the server settings.
But as I have no idea what it might be, I can not find anything in the settings that might cause this behavior.
Obs: The system is made in PHP 7. The server uses apache 2.4 + CloudLinux to avoid abuse of resources by a single domain