The problem is that pd sends it's send-symbol, even if the fader is moved as a result of the receive-symbol. This means that the bcr get's the value right back, with a small delay, which causes the whole to be very reluctent to accept movements from the bcr.
I had to solve a similar problem in a few patches with my bcr2000, so I wrote a few small "helper" abstractions. I wanted to be able to move the controller and have it update a UI element in pd, and vice versa -- and I needed them to be in sync all the time. You can get these two abstractions here: http://noisybox.net/computers/pd/ctrl_sync.pd http://noisybox.net/computers/pd/nrpn_sync.pd
They basically encapsulate the logic around spigot as Luigi suggested. Input the signal from a UI element (slider/ui/etc) into the top and feed back the control output back to the UI element. They're simple, so you should hopefully be able to extend them easily. They're a little stupid in that they assume a control range with 0 at the low end...but they helped clean up some patches and keep things in sync.
-jason