How do you identify which message is causing a policy violation?

We received the following notification in support inbox:

XYZ has been temporarily blocked from sending messages. A message sent from this Page violated our Community Standards or Facebook Pages Terms.

Since this isn't the first time this has happened, the temporary block will last 3 days. During this time, no one will be able to send messages as XYZ. You can still send messages from your own account.

The problem is that it is really difficult to identify the route cause this we have 1000s of new users every day. How do we pin point the issue.

Asked about 8 months ago