Zeiss Distagon 21mm color cast vignetting

Hello,

So I've bought this Distagon 21mm about a month ago and I rarely had the chance to use it. What I shot with it looked absolutely great until yesterday, when I noticed very strong color cast vignetting (especially on the right side of the image, worse in corners). See the attached images.
As I read, I'm not the only one noticing this problem - and it appears in winter scenes mostly. However, to me this looks unacceptable. Even though I can correct it in post processing - for a lens of this price I shouldn't have to do it.
Has anyone here had the same problem? Please share your experience.

Images are shot at f/8, btw. So vignetting shouldn't be a problem.