Breakouts working on different Whiteboards?

Hello, 

I held a workshop today, and I prepared various whiteboards beforehand. My plan was to have three breakout groups working on their dedicated whiteboards simultaneously. But I had no idea how to make the people getting access to "their" whiteboards. All ideas I tried failed. Sending them a link failed, they had to enter a password (?), and a pop-up said, no cursor is shown when more than five people enter the same whiteboard.

All the options are "open", no restrictions, so according to the settings, everybody should be able to use it. Is it possible that ZOOM doesn't support such a situation with multiple whiteboards for multiple breakout groups?

Thank you for your input,

Akki