Hdmi and dp don’t work well together

[acousticmood]

I have an intel i7 in a fan-less box. It has an hdmi output and a dp. I want to use the dp for a monitor and send audio through the hdmi to my receiver. 

In order to get the dp to work on my monitor I had to use another monitor through the hdmi. Then it defaults to “extended displays” and I can use the dp monitor. However when I remove the hdmi and plug in my receiver to the hdmi- the dp monitor thinks that a second monitor is connected. I can’t then open any windows on the dp monitor because it is being displayed on the other “non existent” monitor.

I tried setting the monitors to “mirror” but evidently is defaults back to “extended” monitors once the hdmi is plugged in to the receiver.

Any idea how to fix this?

Thankyou,

George.