I got the CDA-9851R model, and was needing to extend the front panel 3 meters, that did work wit flat cable (the type you use inside computers) but the buttons didn't work. I put on my oscilloscope, and saw that the electronics in the front panel did not drive the cable well, read the datasheet for the IC that sent the data
http://www.zapro.dk/public/misc/PT6553.pdf and the output is Open collector, that means that it does not have the strength to drive the cable properly. I soldered in an 74HC04 circuit and put the signal though two hex inverters, and now it works perfectly.
// Per.