When using the multiboard, I've encountered 2 bugs:

1) Canvas showing incorrect content (from another canvas)

2) Inability to post canvas to user's gallery:

When trying to do so, an error message pops up in the bottom-left corner saying "Failed to create new post. At least one collaborator must be selected to post a drawing."

And because it's impossible to select a collaborator, it's impossible to post the drawing.