Hey, I landed here by Googling the same problem with crackle on the filter knob of the Minibrute 2S, and wanted to leave a note for anyone else experiencing the same.
I was also about to report this as a fault, but then saw a YouTube video which emphasised the importance of the gain structure in the original Minibrute. Specifically, setting the individual oscillator faders at a lower level significantly affects the behaviour and sound of the filter + Brute Factor.
Having tried this out I can confirm that setting the oscillator faders lower does seem to eradicate the crackle. The crackle seems to come from the level of certain mid-range harmonics causing the gain structure to clip (inside the filter? Inside the VCA?) when you sweep past them. You can drop the oscillator faders pretty low (like <25%) and still get a good signal by raising the Master vol.
Hope this helps someone- drop a comment if so!