I'm using Safari and Chrome on an iPad Air 2 to do remote updates on a site I'm working on that uses the Callisto template.
If I open up the Layout manager for the template and try to click on the gear icon to access the settings for any particle in a block, it won't open up the configuation settings popup window - it only highlights that particle.
We found an answer that worked on one site.
1. Uninstall all old Gantry 4 extensions, if any.
2. Disable (or uninstall) all old Rok extensions (we think the culprit is Rokextender).