Same issue here but using a custom Best-Tronic cable for a PRS Custom 50C amp.Getting a buzz when engaged.
Best-Tronic Cable: 5-pin DIN > Amp TRS > Helix Ext Amp input
Command Center: Footswitch 10: 1(tip) Footswitch 11: 2(ring Also tried 1 & 2 by itself but same results.