<p>Why does this happen (circled in red), and how can I fix it? It is making my prints come out horrible.</p>

<p>Not shown in the picture, but the option "Coasting" was Enabled:</p>

<ul>
<li>Coasting Volume 0.064 mm<sup>3</sup></li>
<li>Minimum Volume Before Coasting: 0.8</li>
<li>Coasting Speed 90%</li>
</ul>

<hr>

<p><a href="https://i.stack.imgur.com/a4sB6.jpg" rel="nofollow noreferrer" title="Rendered G-code view of a sliced model"><img src="https://i.stack.imgur.com/a4sB6.jpg" alt="Rendered G-code view of a sliced model" title="Rendered G-code view of a sliced model"></a></p>

I have had a similar thing happen when slicing a large piece that has - in real life - walls of about 2 cm. By scaling it down to 1.5%, this become less than the wall thickness, and the wall was simply omitted by CURA.
In my experience, a model showing gaps
can
have in these locations a thickness less than 1 wall.