with the arrival of nested groups we have started to observe issues with triggers view.
The issue occurs on "Configuration of triggers" screen, when there is more than one page of triggers. The pagination generates links in "triggers.php?groupid[0]=52&hostid=10546&page=2" format (groupid as array in url), that frontend cannot process and it ends up with error:

This only happens when group is selected by selectbox in upper right corner. Without selection of group, groupid parameter is not set in the url and frontend shows triggers correctly. Also if we manually edit url to "triggers.php?groupid=52&hostid=10546&page=2" format (groupid as simple parameter), the frontend works as expected.