Elektor Formant Modular

dear, 
my formant lfo potmeters have a weird range:
slow and very usable from zero (8 o'clock) to about 10 o'clock, but after 10 o'clock it gets fast and it goes faster towards the end of the knob. 

is this normal? 
what to do about it? 
it would be handier if the rate slowly evolved into fast towards the ed of the knob. 

the module is fed by a tiptop uzeus ( +-12v )

and compared to my mfos vclfo the formant lfo output is a bit weak (low) 
anything i can do about  this? 

thanks for the help, floris