Monero hashrate drops when you disconnect your monitor (even if you are on IGP), or the screen power shut down after a while.
Simple disable screen power shut down, and do not disconnect your display while mining.
I tried this but still get hashrate drop. Does the monitor still need to be on as well?
I can't use IGPU as my monitor only has DP input.
There is no need for connected display, but don't disconnect while mining to avoid hashrate drop. I'm using it with remote desktop, no display connected to the rig.
I forget to mention that the hashrate drops as well when you try to monitor your vga sensors. I don't know why.
Funny fact: while you're running GPU-Z sensor tab when you start the miner client it won't affect the hashrate until you don't touch the GPU-Z. If you for example change for another VGA in GPU-Z the hashrate drops.
Then you have to disable and enable GPU(s) again to run properly. Weird bug.