Question about Sigma TC-2001 to 2.0x Nikon

With my Nikon 7100 and the Sigma 150-600 Contemporary, the AF unfortunately only worked up to about 450mm, after that you have to focus from Manuel. The multiple measuring fields don't work either, and so I have already returned the converter... :-(

I have the same lens and the same converter. The autofocus basically works. However, focusing automatically is more difficult. That is, depending on the contour of the targeted object, it works differently. I usually focus manually so that the autofocus doesn't search back and forth for the focus.

Thanks guys...

That doesn't sound good, too bad. What to do now, Sigma lens or Nikon AF-S 200-500mm?