One Voice i behaving strange

Hi,
The 4th voice of my 16 voices is behaving strange.
The SFV filter works fine, but it’s not responding to the ladder filter…
Strange enough it’s working when I change the mode to High Pass of the ladder filter or when I change the slope to 12 or 6 db but then the resonance filter isn’t working..
I already did restore default settings, reinstalled the firmware, oscillator compensation but nothing helped..

Can someone help me?