Not really sure but do you have a seperate set of track feeders for the siding? If so, you could try removing them and then feed the siding from the main line center rail at the switch point end. Inotherwords run a small jumper wire from the center rail on the main to the siding. Keep the insulated joint(s) at each end of the siding. There's no one answer when it comes to the dcs signal. How do you have it wired?
If this is a dead end siding (spur) place a lighted bumper at the end. this really works wonders.