I know the first time I used my Koni in the studio w/90mm "normal" I got a bit of parallax.

I was trying to do head & shoulders with the 90mm ;(

This was a long time ago.

The problem with the 180mm is it doesn't really allow for closer focus.
I know this doesn't address your film issues but just a headsup for you to remember.
The Koni is a great camera for reportage/street but maybe not the best for studio.