Creating Aggregate Template not working

[gottel]

Hi,
I have a problem with creating an aggregate template for the source graph template "Interface - Traffic (bits/sec)". After selecting the graph template from the dropdown menu nothing happends, as you can see in the attached screenshot. All other graph templates are working fine. How to troubleshoot this issue?

I'm using Cacti version 1.1.38 on RHEL7.4

Many thanks
Jens