Is it just the torque converter lock up staying in??
If it stays in, it allows the engine to supply some braking effort, as it would in a manual car.

Turn your music off, and listen to the exhaust note.
When coasting down hill and the foot right off the gas pedal, listen to the exhaust.
Then apply the slightest amount of throttle - not enough to speed up, but just so there is weight on the gas pedal.
If the exhaust note goes quieter at that point, then the torque converter has come out of lock up, and no more engine braking.

Engine braking is good - saves on brake pads.

Not sure if the VX is supposed to do this, but mine does it all the time, and has done since I bought it second hand.

PK