Any web content created from a structure using nested fields in liferay 7.3.5 (or any version of liferay prior to 7.4 I guess) is migrated wrongly.
Steps to reproduce:
1 - Create a web content with the valid web content structure attached in liferay 7.3.5
2 - Upgrade to liferay 7.4 and reindex
3 - Go to edit the web content created, and you will see the webcontent is not rendered so you can't edit. Also it's impossible to add a new web content with that structure
This bug makes liferay 7.4.0. unusable if you're using the old nested fields in the structures.