Describe the bug
As the developer @youknowriad of GBerg asked me, I will now report a new bug: the editor is still slow after the official 4.3 update. I have the feeling that it has become even slower. Old bug that should be solved: #10418

In this article I have already explained what the problem is. Here again the roughest overview:

If you insert an article with a lot of words, headings and blocks, the following happens: the GBerg becomes extremely slow. You can hardly write. It may be due to my internet connection (see here), but I wonder why I can write in all other editors while I'm still sneaking around with GBerg. By the way, this bug has also been noticed by a member of Automatic (see here)

Old Editor:

That's clearly not the same content. Since I can't take the blocks one at a time. I did the test with over 7000 words and the write flow is much better and faster.

New Editor:
http://recordit.co/F7R4jUi7a6 (Please watch the console where you can see that I am writing.)

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Code Editor'
2. Click on 'insert' and insert the following code.
3. Scroll down to 'new Block' and write a paragraph
4. See error: http://recordit.co/F7R4jUi7a6 (Please watch the console where you can see that I am writing.)

Expected behavior
A smooth write flow like the old editor. Without interruptions.

Desktop (please complete the following information):

• OS: Win10
• Browser Chrome
• Version 70

Additional context

• Please add the version of Gutenberg you are using in the description: 4.3 - 4.6
• Wordpress: 4.9.8