What you described is a symptom of a signal issue somewhere between your cable receiver and the Cox server. When you press a button on the remote or use voice control, the receiver sends a command to the Cox server which sends a response back to your receiver. A weak signal can cause a delay in the server response. A lengthy delay might cause a response to time-out and never be received.
Does your cable box ever lock up and require a reboot to resume activity?
Did any of the techs check your signal strength?
Note: Minor delays not caused by a signal issue may occur when viewing near the end of a recording in process.