Ranger – “Defense” [Campaign 5, Mission 3]

I've been stuck on this mission for a week now. I started playing, captured a Castle from Fedei, and divided the army between him and a hired hero. The next day, a message appeared, along with 2 tasks: strengthen the city and free the heroes. Since the losses during the castle capture were significant, I decided to replay. This time, everything went smoothly: there were almost no losses. I sailed to another island, conquered another Sylvan, but during all this time, Violet attacked me only 2 times. This confused me. I checked the tasks, and I only have 3! There's no mention of strengthening the city or the 2 heroes. I replayed 4 times, but neither the message nor the new tasks appear again: confused:
The game is a licensed version, version 1.6, warrior difficulty.
What should I do?:smile45: