Achievement are unlocking after factory reset, achievement before the factory reset aren't

So I've bought a second hand Xbox One twe months ago. Played some Assassin's Creed Unity and Forza Horizon 3 when a friend mentioned that he was getting achievements unlocked. So I look at my achievements and they weren't unlocking after I've done what was
necessary to unlock them.

After contacting Xbox Support and looking at the forums I deleted my account from the Xbox One and re-downloaded it, that didn't work. After that we tried a factory reset of the console, that has actually worked. Achievements are now unlocking but the ones
I've already should have gotten before all this trouble aren't unlocking. I've waited more than 72 hours after the factory reset since that's what the forums say, but the old ones just aren't unlocking. Trueachievements.com also doesn't show them as unlocked.

In Forza Horizon 3 for example I am level 180 but the achievement for playing through the first race. isn't unlocked. Now are simple achievements like that not really a problem, those I can just replay. But there are more difficult ones I'd rather not do
again since they cost a lot of time and effort.

Is there a way to get those achievement unlocked without replaying the whole thing?

:)

 

Achievements not unlocking

Factory reset worked perfectly. Achievements are unlocking.

 

Achievements not unlocking

Update: factory reset worked. Achievements are now unlocking.