I am using a 0.5M cable if I use it with the phone so quite a way away.
HA-2 supplied cable is no longer than my finger and get no interference.
Mojo +0.5M cable = interference
HA-2 + very short cable = no interference
I'm not Mojo bashing just being honest reporting my findings.
I wonder if phone model makes a difference. I've been using a LG G4 with the HA-2 and get some interference.