AE 22.6 GPU preview/render distorted in effect mask

I'm doing a simple curves adjustment with a mask in the upper portion of my frame.  The render is garbled within the effect area.  See attached image. 

When I drag the mask around, the distortion changes- and at one point when covering most of the canvas, it disappears (which isn't the mask I'm needing).  The original footage is interframe MOV from a lumix GH4.

I can turn on Software Only rendering and it goes away.  I'm using Windows 10 with an AMD Radeon RX 6800 card