To view your Accolades in game, open your (J)ournal and tab over to the Accolade section, then scroll down to the STF sections.
If what you're saying above was interpreted correctly by the system, you should have an old version of the Mk XII Set Accolade who's descriptive text mentions both a Title AND a Costume Unlock, and a new version of the Elite/Optional Accolade which mentions only a Title.
Would you mind checking that, and getting back to me? I'm not having much luck reproducing this error locally and need more information.
This is very similar to the "had most of the mk xii ground sets before revamp and then completed the rest after and have every single accolade and piece of gear+ all custome unlock projects completed...but still lists Omega force Operative as IN PROGRESS despite it having all ticks" issue
Which to be honest J-man is probably related. I suspect some kind of legacy issue personally.