Gaplessness....

[simoncn]

MinimServer fully supports gapless playback if and only if the control point and renderer both support this.

To support gapless playback, the renderer must initiate streaming of the next track before it has finished playing the current track. This can be done by the renderer correctly implementing SetNextAVTransportURI or by the renderer natively implementing the OpenHome renderer protocol. As your Sony renderer doesn't do either of these, it is not possible for the control point or the server (or BubbleUPnPServer's software wrapper for the renderer) to compensate for this deficiency.