EF 2x Converter Gone Soft?

After learning to use this over a couple of seasons, this was my go to converter on my 1D mkIII and 300L for field sports. After returning from an extended layoff from shooting, I now find it horrifically soft AFAIK it's never been dropped, nor the pelicase it was stored in, for the last 3-4 years without use. The results are the same on two different cameras, and the ef 1.4 i also use is still sharp. The first two pics are from the last decade and while small files, at least give an indication of what I used to get from it.

These two pics are what i get now...
Any suggestions other than bin it and buy new???