I just had the same problem: (I've received my Polybrute yesterday)
On one of the voices vco-2 did not produce any sound.
On the next voice the Noise generator was not working.
All my calibration's failed in a time-out, both for VCO and Filter
After a few power-cycles VCO-2 is working again on all voices.
The Noise generator is working on all voices, but there is one voice the Noise is only audible through the Steiner-Filter and not through the Ladder filter.
I suspect it is a firmware related problem.
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Now it's the next day:
After some Failed Calibrations and a single Completed Calibration yesterday, all off my voices are working 100% again, vco-2 and noise-gen are audible in all possible routings.
The Polybrute has been powered off all night and is now on for 1,5 hour, so maybe it's not fully warmed up.
Just after I powerd it up this morning, VCO-2 was not audible on one of the voices, and the Steiner resonance was to intense on 2 voices. It seemed to have lost the calibration of yesterday, where the Steiner resonance and cutoff were equal on all voices.
After a restore calibration all is working, only with a slight deviation of Steiner cutoff frequency in one voice.
May assumption is that the calibration procedure needs some improvements.
ps, The PB is the best synth I've ever had, the sound is incredible, the user interface is very good and so simple for the complexity of the synth.
I'm just 2 days into this discovery and it's inspiring, to say the least.