WooCommerce Product Page – Advanced Editor – Page Hanging

I have upgraded Enfold from 4.2.4 to 4.2.6

There is an issue on nearly every WooCommerce site that uses advanced editor for products, where the product page just hangs in white space or gives a 502 error.

I found a workaround by opening each product in turn, switching to default/basic editor, then back to advanced, then saving. All clear.

OK, everything then works again, but I would like to know WHY THIS IS HAPPENING?
I have a test product up on a working site (details in private).

PHP is up to date (v7), and there are no other issues with any plugins.
(problem remains when ALL other plugins are OFF)

Please let me know if you would like access to view this
Stevo :-)