The contents of my whiteboard frequently disappear. How can I resolve this?

The contents of my whiteboard disappear. Usually this just happens on one page and the other pages are fine. Sometimes other members of the room can see the contents of the whiteboard, other times they can't. Sometimes I have been able to get it back if one of the participants who has been able to see it has clicked on the text. Other times this has not worked.

Does anyone know why this happens and if there is any way to resolve it?

Thanks,

Catherine