This is also a problem in WordPress 4.9.x — my developer is already in conversations with them about this. It’s because they’re not triggering existing code in the back end that they are using in the front end in order to remain compatible with 4.9. This is when using the “new experience” Divi builder.
Conversely, I’m seeing some instances where the reverse is happening when using their old builder.
If you have a little time, it would be helpful for you to also reach out to Divi to let them know you are having this problem with ClassicPress. We have also mentioned it. The more people they hear from, the more likely they are to fix it.
If you prefer to work in the back end and want to get back to the old builder, I have a trick you can use to get there from the back end — if that’s useful to you, let me know.
I’ll post here when I hear something else back from Divi — last I know they’d kicked it upstairs.