Hello, I started up the game, and all my stats carried over from Win8/WP, plus the achievements started to unlock, which was great. I got a total of 5 notifications, then they stopped. I looked on the achievement list in the game and it says a total of 19 achievements were unlocked, I forced a scan on TA, and lo and behold, it says I have unlocked 15 achievements, but I have only been given the TA and Gamerscore for the 5 that gave me notifications. The same is shown on www.xbox.com, just Gamerscore for 5 achievements.
I also was able to earn the Supersonic achievement for filling the powerup bar in 10 seconds or less, but this did not trigger any other achievement to unlock.
Some additional info that may help the Devs troubleshoot:
1. For the 4 achievements (First Flight, Everyday Explorer, Last-Second Bingo and Jet Lag) that unlocked in the game but not on TA.com, it originally said in the game that it unlocked on 10/7/2015. When I unlocked Supersonic after midnight, those 4 achievements changed and said they were unlocked on 10/8/2015.
2. For the 2 secret achievements (Last-Second Bingo and Jet Lag), I checked the Xbox One console achievement app and it showed a progress bar even though these are unlocked in the game.
Thank you in advance for bringing this to the Devs attention. I really hope this doesn't drag out like the issues on WP did. :-( That went on for months... (See this thread: http://forums.xbox.com/xbox_support/xbox_mobile_support/f/4282/t/1954113.aspx) I really hope this can be resolved quickly.