I am probably doing something wrong!
try to render first exr sequence (from any source) . Set EXR compression to some cpu intensive choice.
Then load this sequence and in rendering dialog only change name of sequence, so it will create new set of images.
Try last step with patched and unpatched cingg.
A curiosity: doing renderings from both mp4 and exr sequence, the
start of the rendering is always very fast but, coming towards 80%, it
becomes very slow. It basically takes longer to do the final than the
initial 80%. This happens with both appimage and patches.
RAM flushed to relatively slow disk?