Teleconverter: blurred at short focal length

[Mamuang]

Yes, both back and front AT fine tuning. But the problem is that I would have to turn it manually on every time I use the shorter focal length, since at the higher range it's fine (even wide open) and AF fine tuning messes that up.

 

[fmw]

I see... Thanks!
So does it make sense to replace the teleconverter?

Yes. You should replace it with a longer lens.