I think this is one of those bugs that is fixed for some people and not for others. I have played phasma a lot, and with certainty I have hit and even killed with the 3rd strike, and my progress is still at zero on this milestone. I'm sure that I have done this so many times my progress should have completed the milestone by now.
This is one of those problems that's been around for a while. I know it was supposed to be fixed, and it fixed for some people, but not all (not surprising when we see the trouble with lot of fixes on other milestone glitches not working for everyone). Here are a few other reports I found on this issue, though some of these people might have it fixed already.
https://answers.ea.com/t5/Bug-Reports/Captain-Phasma-Milestone/m-p/6719418/highlight/true#M11793
Anyone else still having this issue?
