Good spotting! Faces at the top of the hole were missing. Fixed.

Yay!

Just wanted to say that Angular Brick 1x1 seems to have a gap as well if you're looking at it from the front.

Hello, Are you talking about part 4070?
I tried to have a look but did not manage to find the issue. Do you have a picture that shows the problem?

Here you go: http://mecabricks.com/en/models/1pyj6W0MvRq

I think I understand what you mean. It is actually not an issue. There might be different moulds for this part but all the ones I own have this little rectangular aperture under the front stud. Here is a picture.