Not having the drawings connect to the actual video
If you think that this is impossible, then think again because it has definitely been known to happen. When the animator that is creating the drawing fails to somehow connect them to the video you run the risk of putting out a whiteboard explainer video that will likely mislead the audience and create misunderstanding. Another problem that this creates is that the audience cannot connect to the video in a way that you want them to because of the fact that the drawings are not connected to the video and that is a big problem indeed because that connection between the audience and the video is crucial for them to understand what the explainer is all about and for you to be able to capture their attention. So you need to make sure that each image and scene have a clear connection because that will give the video a seamless flow.