Glitchy HDMI output

I’ve setup my Mars for the first time, and the output from the HDMI is coming through heavily distorted. When the screen isn’t flashing, I can see that everything else about it is functioning as it should. I’m able to log in and use the official Debian image if I work through the display issues.

The distortion changes when I alter the resolution size and/or refresh rate. One monitor displays the HDMI signal with difficulty (giving the message “Signal out of range”), while a different monitor didn’t display anything.

Does anyone have an idea on how to fix this?