Hi, it seems that starting a mission partially disables Disrupt Destiny. Here’s what works:
•targets get marked
•movement speed bonus on killing market targets
and here’s what doesn’t work:
•damage stacks
•headshot kills grant +2 stacks
As said above: It works but the UI won’t show the icon correctly. I had the icon either not appearing at all or stuck at 1 stack and still managed to get the penance for keeping max stacks progressed.