Steps to reproduce the issue

Up until now, this has only has been reproduced on this site:

https://optstroy-prom.ru/

1. Enable Lazy Loading for Images here: https://optstroy-prom.ru/wp-admin/admin.php?page=jetpack#/settings
2. Refresh the site: https://optstroy-prom.ru/
3. You will notice the header gets temporarily expanded:
   

What I expected

The site to load normally. As it does when Lazy Loading is deactivated.

What happened instead

The header got expanded while loading the site and then got back to normal.

Initially reported here: 5419074-hc