We tracked down and fixed an intermittent bug in our Asterisk dialplan where a call could be dropped when using one of the group dial options (i.e. “press 2 for sales”). The issue was that one of our internal IAX peers was answering and dropping the call if it couldn’t establish a SIP channel rather than sending unavailable/congestion. We’ve altered our dialplan to send congestion explicitly when warranted.
This issue did not affect the 24-hour pager option since it always goes directly to a special voicemail box rather than a group dial, nor were direct dial extensions affected.