Ribbon Icons- transferring using CUI Editor

[HC1975]

I've customized my CUI by transferring a ribbon panel from the Geospatial Ribbon to the Civil 3d Home ribbon.

I used the CUI Editor.

The panel tranferred correctly and the buttons function when pressed, its just that the icons do not show. In the help section it does mention this:

"Note: Button images may not appear in the program when you transfer a toolbar, pull-down menu, or ribbon panel from a CUIx file. If the images are loaded from an image file, those images must reside in a folder that is defined in the Options dialog box, Files tab under Support File Search Path or Custom Icon Location. If the images come from a third-party resource DLL, contact the party who created the resource DLL."

Does anyone know if the second scenario, third-party resource DLL, is the issue?