gavinlg
Veteran
It could well be that your camera's RF was slightly off with that lens (this often happens with RF cameras). That will make the lens seem soft wide open when in actuality it is slightly OOF.
re: the biogon - I found it quite sharp wide open, it was more a kind of veiling milky look that was all over the photo at f2. Knocking it up to f2.8 noticeably changes the look. Ive read that the biogons design was stretched to be an f2 lens by the designers and I'd tend to agree with that from my testing.