Yeah, there are some sort of shenanigans going on in the editor. The premade letters use a finer grid than what the editor lets you work with.

It's most obvious with O, {, & and # which are impossible to draw with the grid that's presented to you.

Noticed that on desktop, the real grid, including the "half points" is shown and you can actually work with it. So it might just be a problem with the mobile version.