On occasion with inbound and outbound calls we have issues with DTMF not transmitting properly on our PRI. I'm using an Asterisk 11 server with Freepbx 11 and Inband DTMF settings on the trunk. RFC2833 doesn't work at all.
It's mostly with repeating digits (ie 999) - it doesn't transmit them if you press them quickly - if you go a bit slower it's OK.
Are there any configuration tweaks I can make to adjust the time between tones or something? There's never a problem on the SIP trunks they're RFC2833 though.