"Unknown" Rings all 4 lines

[jfschneid]

Has anyone experienced this? I have a remote user that has a Grandstream GXP2100 connected to her home internet and pointed to our public IP. She has complained a few times about her phone ringing all 4 lines and it say's "Unknown" on the caller ID. When she picks up there is nothing on the other end and it just stops ringing. If you have experienced this and can help it would be appreciated.

Thanks,

 

[leejor]

Is it just a single ring, or does it continue with regular ring cadence until answered?
Are "all 4 lines" the same extension number?
Is the set running the latest firmware?

Is there a record of a call in the 3CX logs?