callingcard wrote:
So it clearly has nothing to do with the browser, operating system on my laptop etc. since these conditions do not change. The only changing conditions are the number of users.
Not necessarily; all useful software performs differently given a different input.
callingcard wrote:
It is probably a setup in php or whenever it is which is not letting the system continue if the task takes more than 30 seconds, or more than 20 seconds or whatever.
So adjust these setting in the upward direction and retest. See the "Resource Limits" section of php.ini.