EGPU disabled when working with Red HDRX files?

Hi,
I'm using Davinci Resolve 17.4. on a Mac Mini8,1 6-core Intel i7, with an EGPU Radeon RX 5700. I'm trying to process a Red Dragon 6K clip in HDRX. I know, that HDR is heavy for processing, but this seems way too much.

I can render a reference HDRX clip with Blend type set to "none" in 2:15min, which is giving me the exposure from the A frames.
When blend type set to "simple" or "Magic Motion" the render time goes up to over 4 hours (!!!). Which is about 100 times longer. It makes no difference if the slider is set to A frames or X frames. It just stays that long.
If I perform the same rendering WITHOUT the EGPU it remains around 4 hours rendering time.

So the question is, is the external GPU disabled, when the blend type is activated and set to "simple" or "magic motion"?

Anyone with a similar experience?

Thanks in advance.

Sebastian

Hello everyone,
I'm still interested in this topic. Maybe someone from Blackmagic could give an answer here.

Thanks,

Sebastian