In the Rackmount forum here; you’ll get more targeted responses in the Stompboxes forum. Is this using a bass guitar? If so, and you haven’t done so already, try setting your Source to Bass in System Settings.
Any particular algorithm you’re using for this? I had the best “power chord” success with H910 / H949 [Modern Type], or the HarModulator. You can pull off the same 5ths / octaves in Diatonic or QuadraVox., without regard to Key / Scale. Yes, the latter two will respond better to monophonic input.
It can help to back off the Mix, and favor the 5th over the Octave with Pitch A / Pitch B Mix. Fine-tune them to be present, yet not fully up front.