It does sound like a HD621-G68 interface configuration error.

Are you using the Config program to make changes? If so, are you saving both the HD621 and G68 changes to the respective devices?




Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.