You are seeing errors in the Directory Integration logs that contain "Invalid search base".
"Directory Data Service - [1508798383334] Invalid search base"
OR
"Invalid query start (base DN) specified for LDAP data source. DDS error code: 800410 Additional information: Invalid search base: example.com"
The cause of this issue is currently unknown.
(NOTE: There can be more than one Customize Query button per tab)