When I draw an 8 it seems to frequently classify it as a zero. In fact, most of the numbers I draw don't get correctly classified. Just the 0's and 1's are consistent.
I found the same thing. If you draw an 8 with more of an 'x' in the middle, it's fine, but if you draw two o's on top of one another, it can't figure it out. I suspect they need to increase the diversity of their training set.