Can’t draw characters right

Hi, guys!
So I’ve decided to create a new font from scratch, entirely on Glyphs.
And for that, I’ve decided to follow some of their tutorials.
But I’m encountering this issue when drawing out the letters. In some areas I find these “little bumps” (as shown on the image below).
Is there any good way to fix this?

Read this please:

What George said. And you can watch the movie too.