If you encounter a cx that reports their screen is showing a "Waiting for Update Media" message on their display that they are not able to make go away, this is the HMI module trying to update itself.
If you have a USB drive plugged in, there could be a loose file on it triggering the update so please be mindful of any flash drives or anything that is plugged into the USB hub.
As a troubleshooting step, try unplugging all the modules within the vehicle (HMI, ACM, anything going to the amps) turn the vehicle off and perform a CAN-bus reset by disconnecting the negative terminal for about 10 minutes and connecting everything again.
If this message continues to show up after this procedure, they will need to take their vehicle to the dealer to have them further assess or diagnose the HMI in case of an actual issue.