Hey, months ago I get the same lens with the same problem, unfortunately I didn´t accept the deal with the seller, which was that I had to send it back to him and pay the shipping, and I kept the lens hoping I would be abble to service it myself. Nothing "normal" worked. I can´t get a focused image in the gh4 and I did some experiments. This is not that the image is soft, it is not focused. Now the lens is servicing in a lens specialized, but they called me saying they don´t know how to repair it.
Any advice? I can send it to a trusted servicing that you recomend, I can not sell or use it now so only way is to try to fix it. Thank you very much in advance!