Retrologue humming sound help?

I recently found that whenever I press E5 together with G5 (E5+G5), a very weird humming sound would appear. However if I only press E5 or G5 alone no such sound happens.
I also tried E5+G5 on my hardware synth (Korg Minilogue), the same phenomenon appears! I wonder if anyone has seen that before? Is there a way to fix it?
FYI:

  1. Iā€™m using Cubase 8.5 Artist.
  2. I put E5+G5 into the key editor, but the strange humming sound still appears, which sounds very uncomfortable and irritating.

a minor third? :bulb: :mrgreen: