I've had this issue for the last couple of months when using Chrome. Different areas of the Gantry 5 interface in the admin have some bugginess, both visually and functionally. Mainly I'm seeing the issues in the Styles tab in Gantry 5 and within some Particles.

In the Styles tab, you can see the visual bug in my attached screenshot. Functionally, there are issues with opening color selectors and image selectors on any modules that are in the right-hand column— mainly, it just doesn't work. Sometimes the color selector will pop open way further down the page instead of where the field is positioned. I have to paste in a file name or a color name much of the time. The issues don't ever occur in the left-hand column, only in the right.

In Particles, I have the issue in any particle that lets you choose multiple items within the particle (an Image Feature particle, for example). If you open all the items in a grid format, then there are functionality problems for any element that is in the right-hand column of the grid. The image selector doesn't always work, and you cannot directly click the cursor into all the text boxes. To get down to the Description field, I often have to start at a field higher up and tab down. The issues don't ever occur in the left-hand column, only in the right.

I don't have any of these issues while using Firefox, it only happens in Chrome. This is a persistent problem that occurs in all Gantry 5 sites that I use in Chrome, and it was present before my latest update of Chrome (currently using Version 67.0.3396.87). I have had the same issue on a Rockettheme site, so I don't think it's isolated to Inspire Themes, but I use a lot more of your templates right now, so I figured reporting the bugs to you was a good place to start.