This issue is that when calls are run through Broadvox and Level 3 the in-call rfc2833 dtmf is not reliable. This occured for me on asterisk version 18.104.22.168, 22.214.171.124 it appears to have been fixed when I went to 126.96.36.199 but broken again in 188.8.131.52-rc1. I have tested with Grandstream and SNOM phones and both fail 90% of the time Unidata phones fail 10% of the time Audiocodes and Grandstream ATA’s appear to not suffer from the issue on any version of asterisk.
What happens is when a caller trys to enter DTMF keys durring a call the far end routed through these carriers do not detect all of the digits. We did captures with broadvox and here is what they have said.