Mass Effect Gunsmith Achievement Not Working

@Mrgaby95 Do you happen to remember which gun you upgraded to level 10 when you got it? Also do you remember when you did it? (ex. Was it right after Priority: Citadel)

So this kind of seems like a terrible work-around to the problem, but I just cleared my local data on my xbox to delete my saves (making Gunsmith show up as 0/10 again), and I'm going to speed run a playthrough of ME3 just to try and get this again. Hopefully I don't run into the issue again. 

Update: So the workaround worked. On my xbox series x, I cleared my local save data then disconnected from the internet to prevent any save-data auto-syncs. I then booted the game and went immediately into ME3 starting a brand new completely fresh character. In the ME3 main menu, I confirmed that the achievement was 0/10 Gunsmith by going into Extras->Achievements then checking manually. I then proceeded to complete the first playthough as normal.

According to my save file it took about 5 hours of game-time to complete the playthrough. I did Narrative Difficulty with a Vanguard Class, running past as many enemies as possible, skipping every dialogue choice when possible, and completing priority missions only. I also acquired the Adas assault rifle and immediately upgraded it to 5.

On the second playthrough I was very careful and probably did more than necessary. I started my NG+ on the main menu, completed Earth->Mars->Citadel->Palaven then went back to the Citadel to make sure all vendors were unlocked (by going into each section and entering every shop menu). I then went back to to the Normandy and very slowly upgraded my Adas assault rifle to 6 -> 7 -> 8 -> 9, each leaving the menu and watching the achievement progress go up. After upgrading to 9 I made a save point, and exited the game. I re-opened the game, went to the mass effect 3 main menu then connected my xbox back into the internet, making sure xbox live connected. I once more went back to the Extra->achievement menu to confirm Gunsmith was at 9/10. I then loaded my save point bought the rank 10 version of the Adas assault rifle and backed out of the menu. Then the achievement popped as normal.

I then closed the game and re-opened it to get all my old save data back. I selected the network (Cloud) save data from xbox and was pleasantly surprised to see that not only did I get all my old save data, but it also kept my newly made vanguard character.

I suspect that this solution will work for every platform (PS4, PC). But I understand not everyone is willing to do a whole playthrough just for 1 single achievement. Hopefully a patch is made that will be able to see that Gunsmith is 10/10, and will unlock if it hasn't already. I imagine a simple script could be made to fix that.

But yeah, hopefully this solution helps someone willing to sacrifice some time to get it.

Cheers