Update: the illegal vertex buffer error still exists for me in the latest update.
Gotcha. Must be some way that the vertex buffer just doesn't get created before the first draw call. When I have a moment I'll add some failsafe so others do not have the issue. Checking if it exists or avoiding drawing for a few steps works for now, but long term something more elegant needs to be in place.
Thanks again for brining it to my attention, since multiplayer is not tested as much.