Now I understand !

After I had uploaded the new firmware, I noticed that the speaker had set itself to 'R. Slv2'. Re-typing to '1' set it back to 'R. Slv.'.

It seems that the new firmware supports two configurations of slave - one that defaults to its D1 input and the other to its D2 input. Not sure why you would want to do that though.

Still not sure of the significance of that error 4 though.

HH1 Photo 34. 598DP, 504, 518, 561(M), DSP5000, DSP33C, DSP33
2nd Room: 541, 555