Its not even a bug. The scheduling in the game is just horribly designed/coded. A lot of leagues, but most notably International Breaks and Cups have hard coded dates into their games. Instead of being dynamic and based on rules, such as Champions League takes priority over everything and leagues being able to go somewhat over their start and stop dates, it's all hard coded.

I understand having it be algorithm based could lead to mistakes and overlapping dates, but it's a could. Unless you're in a league that already have scheduling for all these 50-60 matches in a year it will happen, every single year to minor or major annoyance for the player.

The current system also pretty much lies and screws the manager by asking you if you want to postpone league games due to players being on International Duty, but the game asks this on the day of non EU countries' call ups. So you think to yourself, hey let me play this game despite 3 people missing. Then the next day all the EU call ups happen and suddenly your game is without 15 players. And if you do postpone a game and there's a lack of hard coded game dates left, well guess what, you just get even more games during the next international break.

As fun and addicting this game series is, I'd gladly take a year of no new features for them to just work the entire year on making scheduling not shit.