Did you purchase your cameras from the same place you purchased your NVR? I have a few systems out there that do this. The common link is for some reason the Dahua Cams I bought were from another Dahua rebrander. Ok what the heck I will name names here. I have a local guy I have dealt with, he sold me a Optiview NVR a few years back. I purchased a few cams from another Dahua rebrander (Nellys) and everything works great. Just have the ghost cams like you do and cannot make it go away. I suspect its a firmware issue but I have just lived with it because the end user cannot see or be bothered by this. I cannot let it drive me nuts and not had a lot of time to look into it either. If anyone out there can explain this I would be all ears.