This is happening because of the left and right header padding values. The padding creates a narrow space in which to fit the navigation text. If the text cannot fit, it will wraparound causing the text to break up to fit within the space available.
To fix this, the left and right header padding values need to be removed:
- Go to Style > Designer.
- Under the "Layout" section, click Header Padding.
- For the left and right padding, please remove the values or check "None".
- Click Save.