Component/system involved: Electronic Parking Brake (EPB) system and EPB control switch on my Cadillac CT5-V Blackwing. The vehicle and component are currently available for inspection. What happened / safety risk: The vehicle experienced an unattended roll-away and struck a tree, causing significant vehicle damage. No one was injured, but the vehicle’s uncontrolled movement created a risk of serious injury or property damage. Reproducibility: After the incident, I discovered that I can reproduce a behavior in which the electronic parking brake is released and, if I actuate the EPB switch again shortly afterward to reapply the parking brake, the vehicle sometimes does not respond to that second input. The parking brake remains released and the expected parking-brake indication does not appear. If I wait longer and actuate the switch again, the parking brake applies normally. I have video showing this behavior. The issue has not yet been evaluated or confirmed by a Cadillac dealer. Inspections: The vehicle has been inspected in connection with the collision/insurance claim, but the EPB behavior has not yet been evaluated by Cadillac/GM or an independent service center. I intend to have Cadillac evaluate it. Warnings/symptoms: I did not observe a warning lamp, error message, or other indication that the EPB system had a fault before the incident. After the incident, I discovered the reproducible behavior described above. During an unsuccessful rapid reapplication, there is