A couple of thoughts. I have used this combo and known other who have used it. It's beautiful, a match made in heaven I believe.

Two issues come to mind. Efke was known for coating issues. I have seen them and they have been widely reported here and at the LF forum. Could it be that you are seeing a coating issue?

Or perhaps it is a processing issue? This oftentimes happens at the beginning of development, especially when adding the developer.