[asterisk-users] Always 486 Busy Here for anonymous calls

[jg]

Hi!

I am running an Asterisk PBX 11.6-cert10 with about 20 SIP phones and recently one of the phones 
(Snom 720) always returns "486 Busy Here" when calling anonymously. It's only a single phone, 
the rest works as expected. I checked the phone's settings and there are no differences in the 
configuration compared to the rest.

I do not expect that Asterisk is the problem, but does someone know under which circumstances 
this kind of problem can occur?

jg