[SOLVED] for whatever reason I had missed the extra update. If you go to the link below, this FW pair fixed the gobbledegook screen presentation of RX 950 and now it works perfectly, and sounds great.
So it looks like there was a FW update for the S2400 and DSP that I didnt have - Mikey posted it in the forum but I think when I checked the DOWNLOADS page was not updated, so I didnt know (the downloads support page has been updated now). I am installing the FW files now.