I have just taken my Plaubel Makina 670 to the UK agent for a light leak problem (from my sample negs replacement door seal - Phew and nothing
worse hopefully) I also pointed out an uneveness in the spacing.
Apparently this typically happens at the fifth frame?
Anyway,the good news is that you can,according to him, fix it yourself!
I will double check this info. when I see him to pickup the camera,but it is
all a matter of retentioning a spring as you load a film.
Lets say you have got to the stage of attaching the film to the take up spool and about to wind on to the marker on the backing paper before closing
the camera back.
Before you do this,place the thumb of your left hand on the backing paper
on the take up spool to create tension and start to wind on. Just above the top of the take up spool you can see a spring which as you wind on will retention and solve you spacing issue.
I hope you find this info. useful. I will try and confirm any variation to the
above,when I next have contact with the UK agent.
Please do not rely on it if you are about to take an important sequence of
shots;maybe try the procedure and run a test film to see if it worked.
All the best,Ivan.