Update failed. The json is not a valid json response

Anytime I try to edit a page, I get this error. Initially all pages were disrupted and i had to disable all plugins and activate them one by one to check which was causing the error. I now have just woocommerce and beaver activated and beaver still gives that error. I cleared cache in beaver before my pages were restored but i still cant edit cos it keeps giving the error with a dark overlay over the page in the edit. Kindly assist.