Having been a WordPress fan, evangelist, trainer and user for many years the evolution of the WordPress core and all the plugins that surround and support it have been spectacular. Great things happen with the hard work of all the WordPress users, developers and supporters. It is truly a passion the has, and continues to help millions world wide. That said, I want to aware all my WordPress user friends of a bug that I have encountered. This is to help you with a workaround. I am very confident this will be fixed in a soon to be coming release, although I know not when.
Assuming you have upgraded to the latest version of WordPress and you have written an article in your word processor and now want to add it to your site. So you create a new post and cut from the word processor and paste into your new Gutenberg Post. If you are pasting a few lines, no problem. If you are pasting several paragraphs, You get an error message and it does not paste.
If this occurs the workaround is to install the Classic Editor Plugin by Version 1.5 | By WordPress Contributors and it will return you to the old editor and you can paste away freely. After you are done with the big insertions you can deactivate the Classic Editor Plugin and continue Gutenberging.
This is not meant to be an all encompassing fix, it is just a way to keep everything rolling as we all update our sites.