PC boards prior to Version 3.1 had 2 separate ground connections (Analog Ground and Digital Ground) to eliminate the possibility of digital noise appearing on the audio signals of the RC210. As such, on these earlier boards, both grounds MUST be connected or the controller will malfunction.
On newer boards (Version 3.1 and later), there is only one actual ground connection, even though there are still 2 ground pins on the power connector. Either one may be used
This was changed because the added ground plane on the top and bottom of the pc board have eliminated the threat of digital noise being superimposed on the audio signals.