Hi Dex. I just played Easy level 3 again and I could see no points where I had to guess. I think there are some new strategies you need to work out in level 3 and if you miss one of them that could cause you issues.
For example, level 3 relies on you working out that if there are 2 Xs in a row/column and that row / column has a medial hint, then the medial hint tells you exactly where that shape has to go (as there are only 3 spaces left there's only one square the shape can go and still be in the middle). Did you take that into consideration?