I have completed the game 6 days ago.
About 3 days ago I pressed the 'request Scanner update' button on the game's site.
TSA seems to think I don't own the game. (it does not show in 'My games')
These Users show discrepancies in when they got the achievement and when the game completion was registered:
PLordJdabaDThey both got the last achievement Sep 19 but their completion triggered Sep 24.
(Correction JdabaD got the last one on Sep 20, curiously, the /completionists leaderboard is correct)
What causes these issues? (for this game / in general)