Just bought this lens, works fine except I'm getting a very strange artifact in certain light (not the well-documented problem when shooting into the sun). The problem is a series of slightly arcing waves in the background of certain images. The problem is illustrated in the attached photo (Nikon D7100, raw, minor post processing in Lightroom). I've always used this lens is used with a Nikon 1.4TC (TC-14E). The problem is the same shooting wide open or at a smaller aperture. I'm not sure of the VR setting when I took these pics, I generally turn it off when shooting faster than a 500th, and as I have images shot both faster and slower than that with the same problem, I assume this is not VR related.
This only occurs in specific light -- I've shot a few hundred pics so far as this example is the worst. Note the attached image is cropped, the arcing behavior of the distortion is more apparent when the entire frame is observed.
Is this a known problem, or might there be a problem with my lens or setup? To my uneducated eye, looks like it could be a fresnel-related issue.
Thanks, Jim
PS If any birders out there, the birds are relatively uncommon00 red-billed pigeons, Rio Grande Valley, TX.