Are these all equally grammatic?

It was too difficult a problem to fix.
It was a too difficult problem to fix.
It was a problem too difficult to fix.

Then what about these? The second sounds wrong to me.

It was so difficult a problem to fix, I cried.
It was a so difficult problem to fix, I cried.
It was a problem so difficult to fix, I cried.

I prefer the third choice in both cases.

Geoff D said:

I prefer the third choice in both cases.

ditto

First or third for me. The second seems wrong.

1 and 3 are the same, 2 ‘may’ be grammatically correct but it certainly doesn’t ‘feel right’