OpenCore wake problem with RX550 640SP

I have an opencore based hackintosh built following the dortania guide and derived from https://github.com/zearp/OptiHack. The system has a Yeston RX550 640SP, which is a Polaris21 baffin based card. I have it connected via HDMI to a UWQHD 3440x1440 display which is awesome.

My problem is that if I put the computer to sleep and wake it up. The display doesn't wake properly, I end up with a 640x480 image from the top-left (i.e. the apple logo and menus etc) centred on the screen alternating with a white flash.

If anyone has any clue how to fix this problem it would be very much appreciated.

Thanks.

submitted by /u/pkendall64
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