yes, i seen this problem at different locations, at home, in rehearsed room and on stage. In the last time on Stage, i remember know, i used the preset tape echo for one song. in this song i need sometimes long delay and sometimes not. first i was activate the delay with the left footswitch. in the middle from this song i don't need long delay thats why i press the button again and the h9 was going in bypass. in the ending i was playing a solo and i activate Tape Delay again (left footswitch) in the middle from solo part the h9 turns off.  the connection was good. also when i was at home i use a Voodoo Lab Digital with 12V 400mA and the H9 operate only on one of isolated output. was the same problem. u see, i can not really find the error because it`s alway different.