Mmmmmm..... I would not necessarily trust a computer recording device unless I had tested it on some rapid waveforms before and knew its accuracy. I have used an oscilloscope like Skykeith to see the pulses. If your IVR is really putting out a low voltage of around 6 volts, then the contacts may be be burned inside. Not sure if a contact file would clean it up or not. If it did, I bet some silver plating powder would fix it up..... or just get another one!