Does the G68 also click at that point. When changing DSP mode, the Meridian processors ground the outputs (on 568 and iirc 861 its done solid state, but G68 its done in a relay) and on relay based ones you may hear a click. So going from feature, to advert and vice versa, there may be a change in codec, so output is grounded. This may cause other transient effects such as popping. Worth checking, but I suspect in many cases, this will be 'normal'. I suspect some speakers will be more susceptible than others. When I use to run 5xDSP33 and a sub, some speakers popped more often than others.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).