The synchronization interface response of ABM device is not email address

I have been running ABM to synchronize devices for some time now, but in recent days, when using interface synchronization, the device's "assembly_assigned-by" field responded by the interface has changed. The official website should return "The email of the person who assigned the device." However, what I received was a string of numbers, such as 275xxxxxxxx. Some devices may change the field to email again when synchronizing, but unfortunately some devices will always have these numbers. How can I recover the email?

https://mdmenrollment.apple.com/server/devices https://mdmenrollment.apple.com/devices/sync

The synchronization interface response of ABM device is not email address
 
 
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