Hey!
I have the same problem with the Casanova achievement. Like you said, I tried everything but it just wouldn't unlock on the multiple tries I attempted it. Looking at the comments in the solution, it would appear we're not the only ones.
I just need this and 'Lunar Lunatic' for the completion of this game but tbh, I'm not even attempting that unless a fix is found for 'Casanova'. I'm not putting myself through what looks like a tough achievement if I can't get the completion due to something which
should be so easy to unlock.
One other thing, I tried to get the 'Casanova' achievement on multiple Xbox 360's but I was hoping that if the game became backwards compatible, maybe it would fix any issues. I've heard of games having buggy achievements on the 360 but they somehow work on Xbox One. Anyway, if you've not already voted for the game to join BC then vote here:-
link hiddenSorry I couldn't be of any real help, just wanted to let you know that there are other people in the same boat.