We are having similar issues. We just updated to WP 4.6, and then a lot of errors are coming.
Please take a look some of the error:
Warning: array_merge(): Argument #1 is not an array in /home/XXXXXXXX/public_html/wp-includes/theme.php on line 1557
Warning: array_unique() expects parameter 1 to be array, null given in /home/XXXXXXXX/public_html/wp-includes/theme.php on line 1557
At this point I already test changing for theme, disable other plugins and this one “Event Manager” and “Event Manager Pro” are causing this errors.
Thank you