Duplicate Blendshapes

I run into an issue trying to use FPS Mesh Tool (https://assetstore.unity.com/packages/tools/modeling/fps-mesh-tool-28006) with a CC4 imported character. The tool fails due to a duplicate blend shape "Head_Backward" which exists twice in the meshes' blend shape list. Was wondering if this is an issue cased by the importer tool or might it actually come from the source (CC4)? Any ideas?