Hello,
I have won all the gold medals. When i check in all missions, the game sas that i ve gold medals on each missions in easy and severals other gold medals in other difficulties.
The problem is the achievement hasn’t pop because it says that i m at 90% 
Regards,
I second that. I have all the gold medals and it says 81%.
> 2533274822279366;1:
> Hello,
>
> I have won all the gold medals. When i check in all missions, the game sas that i ve gold medals on each missions in easy and severals other gold medals in other difficulties.
>
> The problem is the achievement hasn’t pop because it says that i m at 90%
>
> Regards,
> 2533274806563958;2:
> I second that. I have all the gold medals and it says 81%.
Apparently for all the achievements like that (I’m having it with skulls and bonus objectives) the issue with cheevos is if you exit from the mission summary screen instead of continuing to the next mission. If you know/can work out which missions you did it for and rerun it might pop.
Let us know: I’ve not managed to confirm myself yet, but I’ve seen people on XBL say it works.