, 04:15 PM
I already submitted a detailed bug report in game about this specific issue. It's not easily reproducible (as it requires a fresh legacy and fairly high level chars), but as the mirror mission on either side shows the same problem (Javaal and Saleucami are BOTH stuck in my tracker), I'm fairly certain the issue is this:
1) Track either those missions through the achievement trackers.
2) Complete the mission with all the required objective except the bugged one, which has no way to be completed
3) Even though you will not receive any success notification, the achievement will show as completed in the achievement panel (even the bugged achievement will show as completed there)
4) Due to the achievement being now complete, the track/untrack option disappears and the bugged objective remains in the tracker "forevermore".
I'm fairly certain this happens to everybody, as I've heard reports of the missing achievement notification. However the bug itself is difficult to notice because it will leave no trace afterwards unless you had the achievement tracked at the moment of completion.
If I had to make a guess, I'd say that the way the achievement is internally tracked is correct (as in, it completes when it should), however the text of the objectives is wrong and when the achievement is marked as completed it probably automatically sets the text to "complete" without actually touching the redundant objective, which doesn't get automatically removed from the tracker and it can't be removed by untracking anymore as the option is not there.