Here are two possible solutions for you:
1. The next time the black screen shows up, press ALT + ENTER to toggle fullscreen (for Windows) or CMD+F (for Mac).
2. If you are using a laptop with a plugged in monitor, try using the laptop display only.
If issues continue please contact our support team and in as much detail as possible describe what has been happening, what you have tried and the specifications of the device you are using.