I am having the same issue controlling an RX1052 via 232/RP6. I just took a look at the RJ45 input documentation again and it looks like they document the RJ45 pin layout in reverse from the standard telco layout. The Rotel diagram indicates with tab up... facing the plug... pins 1-8 run right to left.

It looks like I may need to rewire my RJ45 to DB9 adapter to reflect this. I, of course, assumed that pin 3 was just that and not actually pin 6.