This is a pretty basic one and I'm surprised it has not been reported yet but I didn't find it in the known list or on previous posts.
Tokens are auto-scaling only using the horizontal width and not the longest side. This means that portrait images (which I assume are most dimensions) are going to exceed the upper and lower boundaries of the grid. The 80% and 100% options work fine, its just that they only use the one dimension. I'm not sure if this is simply an oversight or if it is a limitation. This hold true for all grid types, square, iso, and both hex.