Hi welcome to the forum. What do you mean when you say "known issue"? The board is supposed to mute the signal when it switches that's what makes it clickless. If you don't mute the signal then when you switch you can get a click if the levels of the signals you're switching are different, muting the signal, switching and then unmuting it stops this happening. I haven't seen the schematic but Q1 and Q2 must do the muting.