Hi,
Your hosting provider WpEngine added as MU plugin the condition to kill automatically so called long queries (longer 16384 characters) having database productivity in a mind. This is a reason why a restricted user does not see categories list.
My own thought: It is quite good to kill some ineffective query if it takes too much time at the database server to fulfill it. But it’s not a good idea to measure query productivity at the client side just counting characters inside a query string.
Returning to the problem, query is so long due to Yoast prominent words. Yoast product saves them as taxonomies and currently you have 4108 taxonomy db records automatically created by Yoast. (Some times it seems to me that not SEO exists to enhance the Internet usability) but all around exists to work for SEO. It takes too much resources.)
I will look how to exclude Yoast related taxonomies from a queries modified by URE Pro without having to list them all by ID. I found the related discussion about problem created by prominent words taxonomy for other plugin.
