Here in this General Discussion thread multiple people have reported their career mode getting stuck at a certain percentage, with no new races available despite all previous events being marked as complete (all Green and Gold).

The problem seems to be that the unlock percentage does not increase unless the player gets 1st place in every race, even in events which do not require this. This applies to:

1. Multi-race events where you can get a Gold Cup even without being 1st in every race
   
2. Events which give you a green mark for getting, say 3rd position or lower

This ruins the game because you can easily get stuck in a situation where you thought you fulfilled all requirements, but it turns out you had missed 1st place earlier in the career, and the game gives you no indication that this is the problem and which specific event you must retry.