I am having the same issue and have found that the problem may be related to certain content; in my case, parentheses/brackets. I tested pasting in the content of a single page that was giving me the same error as the OP – watching to see when the “Element preview” would fail to load (which appears to be a good indicator of when a page is going to fail to load the builder the next time the page is updated or published) – and found that it was when a text block contained many pieces of text within parentheses (in my case, three instances of parentheses in the text block) that the block would fail to preview and the page would fail to load the page builder as soon as the page was updated/published.

There seems to be some problem that leads to the the page builder failing to load when it encounters certain content, which is why it only occurs on certain pages (another site I built in Enfold has this same behaviour on a page that uses a code block to embed an iframe for a Google Calendar). It seems somewhat finicky as to what content causes it to fail to load.

edit: Here’s how unpredictable this can be: I re-wrote my client’s content to avoid the parentheses I mentioned above. SO, I move to the last of the text that has to be inserted – lo and behold the text fails to preview and does not include three sets of parentheses like the text that caused the issue higher up on the page. I am still trying to discover what characters are causing the issue (I am pasting this text all as straight text and formatting it in the editor, by the way – no strange characters or formatting.)

edit2: this time, it was an apostrophe in my client’s write-up that caused the problem.

edit 3: My conclusion, and I hope others find it helpful – check your content for any characters the system might be misinterpreting or failing on.
To the devs @ Kriesi – you may wish to look to see if there are any characters the page builder SHOULD be interpreting correctly but is failing on (the problem I ran into with a text block having three pieces of text in parentheses and causing the entire builder to fail , in my opinion,should not be intended/accepted behavior!)

• This reply was modified 7 years ago by electris. Reason: Added final thoughts for others who find this message