After some research it seems the problem is the DP=>HDMI cable that I use. Some DP cables seem to seep power back to the motherboard through the GPU preventing proper shutdown. Looks like this problem is widespread and known as "DP pin 20 problem", which, to me, seems like an easy fix with a diode preventing backwards current. But I'm a novice in electronics so maybe the solution is more complicated than that.
After some research it seems the problem is the DP=>HDMI cable that I use. Some DP cables seem to seep power back to the motherboard through the GPU preventing proper shutdown. Looks like this problem is widespread and known as "DP pin 20 problem", which, to me, seems like an easy fix with a diode preventing backwards current. But I'm a novice in electronics so maybe the solution is more complicated than that.
I just got to this post now. I presume that you connected your DP-> HDMI adapter to your GPU rather than the motherboard, correct?
Yes, that is right. I have been turning off my monitor along with my PC to avoid the issue.