Finished the base mesh

I would say the base mesh is finished so far. It needs some details but before that I have to fix a few mesh problems which confuse the hell out of me.

The screenshot below shows one problem that I don't know how to fix. It doesn't seem to be the normals, and I am fairly sure there aren't duplicated faces and/unwelded edges or vertices so I am really stuck for now until I can fix it. It might be harmless but it looks worrying especially as I don't know Max that well.