Using a 2017 HP Spectre with Windows 10 Hooked up to a Samsung TV. In fullscreen mode in both resolutions the signal to the tv cuts in and out. When in windowed mode it works fine on the tv. Fullscreen works fine on the laptop when HDMI is not plugged in.
If your image is cutting in and out, it almost sounds like it could be a problem with the HDMI cable. Maybe the fact that it’s only happened in Fullscreen mode is coincidental. Have you tried using a different HDMI cable to see if that fixes the problem?
If that doesn’t help, please submit a support ticket if you haven’t already done so, and one of our support agents will be happy to take a closer look at this matter.