We're sorry for the inconvenience! It's a hardware-related bug that only a few people experience.
- Update your operating system (Windows or Mac)
- Restart computer
- Windows only: update you graphic card drivers or other manufacturer drivers you might be using.
We're using the operating system's libraries when rendering previews, so if an issue like this happens it usually points to some driver problem.
If this does not help, please let us know.