What are the main reasons people repeat Finnish A1.1 to A1.3 courses and have a hard time moving forward with book 2?

Repeating the Suomen mestari 1 course seems to be a common theme when people share their experiences learning Finnish, myself included. After abandoning my Finnish learning journey for a few years, I finally came back and started from scratch, even though I had finished book 1 years ago. Luckily for me, this time I managed to find a learning system that works, which makes me feel ready to move forward with book 2. After hearing that some of my classmates are considering retaking the class, I would like to understand the main struggles people face when learning Finnish. Will they be similar to my experience, or something different?