The issue is most likely caused by this element
Notice how it’s outside of the #main element? We use some javascript to position the topic-progress widget that’s based on the difference between the height of the #main div and <body> tag.
This element in your theme is interfering with that.
I’m assuming that the element is added with JavaScript. So, remove whatever JavaScript you’re using to add that and add the HTML directly to your theme if possible.
Add this in the common > footer tab
<p style="text-align:center;">
<a href="https://m.do.co/c/06a568f6937f">Hosted using Digital Ocean</a>
</p>
This should give you the same results without interfering with the topic-progress widget.