Thank you for this call example, we were able to locate some historical data and it appears your device is incorrectly sending a malformed ACK, therefore not moving the dialog to a 'confirmed' state, so there cannot be a T.38 reinvite. Have you checked for updates to your device's software or firmware, as this issue may be resolved by an update to fix bugs such as this. Otherwise, you may need to contact your device vendor/manufacturer for more assistance with these malformed acknowledgment packets.