I had same problem on one content heavy page with many <p> tags. However it was not due to reusable blocks yet it was because of number of revisions that page had (more than 500).
So just to leave comment here if reusable block tip above doesn’t solve problems you can check the number of revisions page has.
BR,
Dusan
I can confirm that it works for me as well.
There is no difference at all. You can activate Multisite feature from the regular WordPress install by editing wp-config.php.
Cheers.
