Thanks for your comments;
Yesterday I contacted OPPO Customer Service and received the following reply;
“Under playback setup you will change SACD Priority from Multi Channel to Stereo. The player will then playback the Stereo layer or a SACD”.
I also checked the layout of remote control, there are 35 buttons listed but I do not see any button for selecting the SACD Stereo layer on the remote.
So far so good, the only remaining question is PCM/DSD. On page 60 this is discussed but the choices listed are for HDMI output, in my case I do not want to mess with HDMI but instead use analog two channel RCA outputs.