Trouble with DTMF on outgoing calls.
Played with DTMF transit types – AVT is the type we want (RFC2833), but some digits are not being picked up. In particular, the number 2 is very rarely being picked up.
The solution: reduce the FXS input gain (on the System tab at the bottom). It was on -3. I set it to -5 and it looks perfect. The tone signal must have been clipping.