Why is my back camera focus not working?

The camera of my LG G2 is not working properly anymore since I dropped my phone. Every picture is blurry. The focus of the back camera is not focusing. Software I use: CM12.1 (Nightly).

Things I tried:

• Replacing my camera with a replacement camera from ebay, but it didn't fix the issue.
• Tried StockROM from LG, Version 5.0.2 (Lollipop) and 4.2.2 (KitKat), Manual focus of stock camera app did nothing, automatic focus is not working
• Tried OpenCamera-App
• Tried the camera without the back cover glass (to exclude scratches on the surface as reason)

Has anyone an idea?