You might have issues with images, due to a bug from Google Docs. Copy/pasting images from their API is unreliable as this stage. We have reported this right here
and have introduced a feature request right here
. We are actively monitoring any updates from the Google engineering team and will ping you as soon as we have more information.
I'm really sorry for that. In the meantime, you should be able to merge images that are publicly available online (e.g. use "Search images" or the "URL" tab when inserting images).
Lucy - Customer Support