Thanks for taking this on. I summarize this as a simple cross-fading issue. When a zone is unlinked with any other, the cross-fade works as I set it in the zone's options. When I link it to any other zone, cross-fading and intra-track seeking fails to work correctly. My goal is to get cross-fading working when zones are linked.
I don't know what a client PC is, so I'm pretty sure I don't have that. I have one HTPC that use primarily to play music in various zones throughout my home. I use Gizmo to find tracks and control the player, such as skip the current track. As far as I know, I've never used any form of media network, nor do I transmit music to Gizmo or any other device.
The description of my configuration showing HDMI, TOSLink, Firewire, etc. was to illustrate that I have different levels of sound quality I expect in different zones. I have an Onkyo TX-NR906 in the living room, so HDMI is the best way to get multichannel audio to it. I have pro audio gear in the studio using Behringer FCA610 audio card and balanced audio cables, so firewire from the PC is the best form to send audio.
I listen to music everyday in the studio. Some days I wish to play the same music in the living room or on the deck, and that's where the trouble starts.