Not sure if “double shot” is exactly the name of the skill, but it’s the one where you can shoot 2 bullets at once on the same target.
The bug I noticed goes like this: after you use it once in a map with a character, the second time you try to use it with the same character in the same map - it only delivers (and only consumes) one shot. I noticed this in Stalker Trials and it happens with both characters that have the skill.
