Please do try these troubleshooting steps that may help.
- Start by doing a hard reboot with the TV connect to the laptop. Remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try it again after the reboot.
- If these doesn't work try to uninstall/reinstall the graphics card driver.
- Go to Device Manager and uninstall the graphics driver.
- Check Programs and Features as well and uninstall anything related to the graphics card.
- Once done, download and install the latest driver.
- Reboot your laptop once the latest driver has been installed.
- After the reboot, do test it again and see if the same problem will persist or not.
- If it does, try a different cable for your external monitor or even try a different monitor with your laptop.