Start the editor preview on Stratis (coordinates in the description)
Spawn as default rifleman unit
Copy position and direction from video
Press X to go crouch
press ; to change to the pistol.
Now walk backwards along the same path as on the video.
Going to combat with C will cancel the bug
Changing to Rifle will cancel the bug.
Walking forward doesn't trigger the bug.
There are other areas at that compound that produce this effect, just walk backwards around, somewhere next to sandbags.