Pop going to or above Ab from below in unison

[catawboy]

What's the reason for the pop when crossing above the highest G (when in Transpose 0) on the keyboard in unison mode? Noticed when fiddling with the Lucky Man solo. The pop point moves with transposition, so Transpose +1 moves that to the next octave down and so on, so not the keys part of the hardware I guess. Once you've popped, it does in fact stop, so isn't pringles either - as long as you remain above G. If you go below Ab, it resets and crossing above G again pops.  More noticeable with legato playing, but it does not seem to depend on Glide, nor can I filter it out.