When the speed brakes are deployed during descent in the PMDG 777 and the yoke is turned to the right to bank right for example, the speed brakes on the left wing go all the way down. There is no middle-ground. i.e. the spoilers are either fully deployed, or fully retracted during a turn.

 

However, in the real 777, turning the yoke right while the speed brakes are deployed will cause the speed brakes on the left wing to go slightly down depending on how much the pilot turns the yoke. If you look at this video below at around 42:05, you can see the 2 furthest spoilers, and the two spoiler panels closest to the camera retract slightly as the pilot turns the yoke. You can definitely see this in HD and in full screen. This can not be recreated in the PMDG 777 however because the spoilers would just flap up and down instead of retracting slightly.

 

I assume your speedbrakes are deployed only to 50% extension on descent?