I can confirm this weird sound on my Axe FX II Mk 1, Q3.02, on both the Ch2 and Ch4 V4 silver (but not on Ch3). Interestingly, the buzzing goes away by reducing the value of "Triode 2 Plate Frequency" to a lower value than the default 40.000 Hz. I chose 6200 Hz, which is the same value as for the blue V4, but in fact any value lower than the default works.
