I understand this thread is old, but I'm having a similar problem with the remote host with three HDMI displays attached, but power is physically removed from the monitors using a smart outlet. Remote Utilities works fine when the monitors are powered, but I can only view/interact with the primary display when power is removed. Turn the power back on, and everything is like it should be.
I've tried updating the host and viewer and selected the legacy capture mode without luck.
Are there other suggestions you have that might help in this situation?
Thank you.