The short version is that one of the filters popped out of the wheel. It was reinserted with an adhesive by a professional (but not Sony). The wheel was working fine, but the adhesive broke down (probably due to heat). It has created a film that covers some of the internal elements. I'm having it cleaned now, but the ND filters are no longer usable. To replace through Sony, it will cost over $700 with parts and labor. I am looking for the new (or used) wheel with filters. Currently, I do not know the part number, as it's not listed in the Sony service manual.
Ryan Abreu, I had the same problem with the ND filter Wheel, but in my case the filter that popped out damaged the "pre sensor" ( i don't know if is this the name, but its the glass that comes under the ND filters wheel).
I found a page from sony that seems to be for replacement parts, but, as you, I didn't find the part number, so, today I tried to contact them, explain the situation and see if they could help.