So you are on WPEngine ?
one good thing about wpengine that it tries to give the maximum performance. one of the biggest rule at their Logic is caching. it simply
caches anything and everything
Sometimes we process a database query the query return old cached date . sometimes you may edit a PHP file and run it and find that the modifications didn’t take effect
as an example when the plugin posts from a feed it checks each link to find if it was posted before or not by simply checking a table for this link existence
even if this link exists the query returns nothing and let the plugin post it again.
WP Engine is not bad but it does not suit our case and I always receive complains from it’s users.