I has a strange experience recently that I can't explain. We're running CCM 3.3.2c. The PSTN gateway is over a 6608 PRI. Everything was working fine.
I swapped another blade in the 6509 (actually the ethernet blade that the CMs were connected to) but did not reset the switch. The CMs were disconnected for a few minutes during the board swap, but were also not restarted. The PRIs remained connected to the 6608. When everything was connected back together, everything appeared to work correctly (calls completed as expected incoming and outgoing).
But it soon became apparent that DTMF tones from the 7960's to the PSTN were not being sent DURING calls when 0-9, #, or * were pressed. The call would complete, but if buttons were pressed during the call, no tones. I tried this to PSTN POTS lines and spoke while pressing keys. My voice was sent fine, but no tones. This was true for all IP phone users. G.711 everywhere. I eventually reset the whole switch and all was well. No errors in the switch log.
I'm at a loss to explain why I saw this behavior. Any idea what would account for this?