This is likely being caused by the theme including a “buggy”, in my opinion, HTML5 shim script. The purpose of these shim scripts is to enable HTML5 features in browsers that do not support them. They work pretty well … but, there seems to be a bug in this shim script.
When you click on a category, the “Search” placeholder string in the search box is being sent as a search keyword term. So you’re actually searching for “Search” within the category being selected. Obviously not what we want to do.
The fix will be to remove the “Search” placeholder text. To do this easily, we can use another plugin.
Changing the search string can be done with the Say What? plugin.
It’ll add a new Text Changes menu item under the Tools admin page.
Click Add New, enter the string exactly as shown in Connections, Search.
Next enter connections (notice the lack of capitalization, that’s important!) as the domain and then enter your new text. In this case leave it blank.
That should fix it.