I'm seeing a very similar issue to intel/intel-vaapi-driver#13 in this driver as well, which I was able to replicate using the file linked here: https://docs.google.com/uc?id=0B9X316MN6HHvSlNWb1ZhSGo2X2M&export=download
This is on Ubuntu 18.04.3 (kernel 5.0.0-31-generic), with intel-media-driver/19.2.1 and a Kaby Lake G processor (https://ark.intel.com/content/www/us/en/ark/products/130411/intel-core-i7-8705g-processor-with-radeon-rx-vega-m-gl-graphics-8m-cache-up-to-4-10-ghz.html). @carpalis was able to resolve this last time.