Re-posting from the developer thread - since @saguaros said this is the main thread to follow:
IF you really, really need to make an edit (probably a minor edit) and you can get to your Joomla database...
proceed with caution and do not proceed if you do not know what you're doing
You can go into phpmyAdmin or similar tool, find the table: <prefix>_jabuilder_pages. You should be able to identify the page you want to edit in the field "title".
The html for the page is contained in the field "content". Do not edit in place
Select the field and copy the text to a clipboard or notepad++ (or similar). Find the text you'd like to edit. Change it, save it (just in case). Copy the text from your editor and paste it back into the field "content"
This is for emergency editing of critical (and preferably small) changes.
Hope that helps someone.