Hi
Welcome to Microsoft community.
I'm glad to help you.
Generally speaking, changing from copy to extension, if a freeze occurs, is usually caused by the resolution setting parameters of the two monitors and other display settings being different. You can first set the resolution of your TV to the same resolution and scale as your computer screen to check if the problem disappears.
If anything is unclear, please do not hesitate to let me know.
Best regards
Derrick Qian | Microsoft Community Support Specialist