Client Monitor is out of sync with Program monitor / audio

I am Mercury transmitting my video feed to an external (client) monitor via HDMI cable. The video in the program monitor is in sync with the audio, but the video being transmitted to this external client monitor is out of sync with that audio. This external monitor is what the clients see, and it can be odd for them to see everything out of sync. Is there a way using offset settings to get everything (audio, program monitor video, and external monitor video) to all line up correctly?

Changing the TV's settings to "game mode" as I've read on another forum had no effect on the delay.

Thanks!