1st Bug: The trader remains at the trading post, causing the days left to stop decreasing and also stops new traders coming to the trading post. This also affects the crop rotation for the following years, as the crops get stuck on the current year. A temporary fix is to save and reload the game. After reloading, the trader will be gone, new trades will appear, and the crops will rotate to the correct year.
2nd Bug: On 12x12 fields (uncertain about other sizes), field maintenance works even if no workers are assigned to the fields.