how to fix hdmi output resolution not holding on android tv box

[Android Central Question]

I am running my V3 box on Android 6.0.1 through an HDMI matrix. if i set the display output / HDMI Primary to 1920x1080p it works fine until the box is put into standby. when it comes out of standby it is defaulting to 4096x2160p as this is the max the matrix can handle but I only have a TV capable of doing 1080p. This is not set to auto and i can't work out how to make it stay on 1080p please help