Issue with centering multiple choice navigation buttons

The navigation buttons on the multiple choice slides become left-aligned, and I don't see a place in Properties where I can change it. When I add a new slide, the new one will be properly centered. When I delete the old one, the new slide becomes left-aligned again. I did a screencast so you can see what I'm talking about.

https://youtu.be/Iqct9lubk-Y

I'm using Adobe Captivate is 2017 Release, version 10.0.0.244 on macOS High Sierra. The font is Helvetica.