Hi J C!
Sorry to hear that elements from your slide are missing when previewed or published. Happy to help with this!
Testing your file on my end, I was unable to reproduce the same behavior. While previewing the entire project, just the slide itself, and after published to Review 360, all buttons and images displayed as expected. So yes, I would suggest performing a repair of your Storyline 360 installation to see if that improves the issue. Also, it's recommended to author your courses on a local hard drive, as network or shared drives may cause erratic behavior.
If you're still running into trouble after following those steps, please connect with our support engineers through a support case. They'd be happy to continue troubleshooting with you!