Issues with Video Sharing during Webinar

[PnEvents]

We need to share short video clips at the start of our webinars. I join as the Host and have tried a standard screen share and sharing via the video gallery (advanced settings) with both share sound and optimize for video clip checked. Sometimes it works, and other times the audio does not work. Attendees also see grayed out boxes where my control panel is. How do I fix these issues?