On login modal window 'loading' for about a minute calling datalogstatus.php

Hello,

on a ispconfig 3.1.2, when logging a modal windows appears to be doing something for about a minute before being able to start working with the panel. It does it only once, just after entering user and password and hitting the button.

I can see the modal is a jquery calling every few seconds datalogstatus.php, but don't know what it is that takes so long.

How can I debug it?