Some achievements, if tracked, will not be removed from the Achievement Tracker:
Saleucami Fleet Action Mastery achievement is bugged and stuck in my tracker list as well.
When I "completed" the achievement, I did not get a pop-up, though the achievement is listed as complete and all points are correctly tallied.
And, a further note - the date stamp on the Saleucami Fleet Action Mastery achievement now says whatever the current time is, i.e. every time I click on it in the Legacy window, it updates the timestamp to the current time.
It seems as if the pop-up not firing and the lack of removal and the time stamp are all related, like the achievement is not firing all the processes that should happen when completed.
My Saleucami Fleet Action is stuck as well. I tracked it, completed the mission, it's now marked as complete in the Achievements window but the tracker still has one of the requirements as 0/1. I submitted a ticket in game and received this response:
Your Ticket# 9208904
I am Protocol Droid M0-T0, Human-Cyborg Relations.
Thank you for contacting us about the issue you encountered. This particular case appears to have been caused by a bug within the game that will need to be corrected in a future game update and as such, cannot be corrected by Customer Service.
Because the achievement is complete, the Track button is gone, so I can't untrack it and make it go away. The only way to get rid of it is to turn off the Achievement tracker on my UI or in a space mission, which is annoying for other reasons. Hopefully this will get fixed... it seems like the easy option would be to just re-enable the Track button even on completed achievements, so I could turn it back off myself.