I don't know if this helps but I was perusing the technical bulletins awhile back and remember seeing this. I don't know what timeshift operation is but it may be what you are talking about.
#08-08-44-019D: Intermittent XM, Blank Display, System Resets,
Timeshift Operation or Music Copy Functionality, Incorrect Dimming Level, System Stating Unable to Plan Route After Route Deviation, Radio Locks Up After - (Sep 15, 2009)
Subject: Intermittent XM, Blank Display, System Resets, Timeshift Operation or Music Copy Functionality, Incorrect Dimming Level, System Stating Unable to Plan Route After Route Deviation, Radio Locks Up After Destination Download, System Intermittently Not Showing Low Fuel Warning (Update Navigation Radio Software)
Models: 2008-2009 Cadillac CTS, CTS-V
Built Prior to VIN Breakpoint 90165754
Built Prior to 03/25/2009
Equipped With Navigation Radio (RPO UAV)
Condition
Some customers may comment on any of the following concerns:
• Intermittent XM operation.
• Intermittent timeshift operation.
• Intermittent music copy functionality.
• Intermittent blank display (no text, intermittent touch control).
• Incorrect dimming level (night dimming during day or day dimming at night).
• System stating it is unable to plan a route after a route deviation.
• System intermittently resets (shows Cadillac startup animation).
• System intermittently not showing Low Fuel warning.
• Radio locks up after OnStar® Destination Download (ODD) usage.
• Radio that was turned OFF on the previous ignition cycle may turn ON.
• Date configuration screen displays MM/DD/YYY when DD/MM/YYY is selected.
• Clock configuration displays "Année" for the year.
• Weather information display is slow.
• An Emergency Broadcast System alert may cause a system reset condition.
• Traffic information doesn't include highway entrance/exit.
• Traffic announcement is incorrect.
• Traffic announcement is given while radio is OFF.
• Point of Interest (POI) list only displays Thai restaurants.
• System displays Florida's nearby POI when user selects Nearby POI. Screen displays 3D sky and ground.
• Voice guidance is given at the beginning and arrival when voice guidance is selected OFF.
• Time shift key doesn't work.
• Time shift buffer increases while XM has no signal.
• Screen transits to power OFF after audio SW update.
• Audio hardkey (HK) press is not available while user is pressing "+: holding HVAC HK.
I don't know why, but I like to occasionally look up what types of problems customers are having with their cars
