This clearly looks like an issue on the provider side. The provider should be sending DTMF attributes tot he CUBE. If the provider doesn't send the DTMF attribute then the DTMF tones are sent inband which doesn't always work, specially if any codec o...
You can try copying the IOS image on a usb flash drive and plug it in an available usb port on the router. Then enter 'dev' command to see if the router recognized the flash drive.To boot from usb try 'boot usbflash0:image.name or usbflash1:image.nam...
If you reload the master then whole stack will reload and boot up with the new image. You can also try reloading one member switch at a time by using 'reload slot stack-member-number'