My guess is the item is no longer for sale. It sold via a PM shortly after it was posted. The seller apparently can’t be bothered marking the item as sold or responding to any inquiries.
Came up with one more thing that May be the root cause of your problem..your sd card write speed capability. Are you using a class 10 high speed sd memory card? When I got my D7100 I ordered the fastest card I could get to avoid the type problems you are experiencing based on the recommendations in the owners manual. I did that because my old Olympus walk around camera would get jerky video when the buffers overflowed and I know the importance of this. Also don’t buy cheap cards off eBay. I got a couple of Samsung memory cards from eBay that were Chinese knockoffs. So many write errors I checked with Samsung and found they were not authentic. I threw the garbage away and ordered new ones from B&H which work great.
There is a setting in the setup menu called “flicker reduction”. I don’t shoot video so I never used it but the books I’ve read for the D7100 indicate it affects video flicker on playback depending on the frequency used by the local power company. The instructions indicate try either of the two settings 50hz and 60hz and see if either makes a difference when playing back the recording made under each setting.
I enjoyed reading the Ken Rockwell review of this lens. However his review indicates the lens is readily available and it’s value is as of Feb. 2018 at about $100. Any chance your price will change?