Hi there!
I have seen a little "problem" using i-mscp with pagespeed apache mod and panelredirect.
The pagespeed is minifying some js in a wrong way (eg lets encrypt page) and so the site is not working a 100%.
As "ModPagespeed off" does not work on a per domain basis, I have to check what we can do in this case.
Work-around 1: Simply access the i-MSCP portal page with the direct nginx url:port (8443 or 8080)
Work-around 2: Disable ModPagespeed in you apache2.conf and enable it using .htaccess:
i-mscp 1.5.3
debian 8 and 9
apache 2.4