The transaction was flagged for review due to "suspicious activity" or high-risk geographical locations.
The code "u0407" doesn't directly correspond to widely known or publicly listed Western Union error codes or transaction codes as of my last update. Western Union's system of codes can be extensive and sometimes specific to the nature of the transaction or the service used.
: User reports suggest this specific code may be triggered when a receiver is flagged for receiving funds from multiple overseas sources within a short period. Regional Monitoring