Unfortunately, it has very little or nothing do with the ADSR, and is only happening because of the Decay setting on the Synth Page. This was covered in a previous thread here Inconsistent clicks (analog machines) - Elektron Gear / Syntakt - Elektronauts. So, messing with the Attack, Release, or Amp Retrig on the AMP page has little to no impact. Obviously if you move the Attack to like 100% there is no click because there is no sound, but say set it to 80 (Half way) and you will still get the click. The only counter I have seen is putting the filter to 20 which does remove the click but also removes a lot of the character of the sub.
It is explained at length in that thread, and a poster sort of defends it as a feature. Maybe it is my lack of familiarity with mono synths (I don’t own any mono synths), but it does not seem very good to me.
I have been able to avoid this cutting into sound design in all my other adventures with the syntakt, but the sub bass sound is definitely affected by it.