Arnold stays 'Generating scene' - does not render to disk either

[phillips.a.adam]

I'm using Arnold 5.3.1.1 with Houdini 17.5.258 (Indie)

I'm rendering a single 4k frame and I have an issue where Arnold is firstly refusing to render to disk...It starts just fine and then after 20mins quits the render. When I try to get around the issue by rendering in to the render view Arnold seems to get stuck on Loading the scene to the frame buffer - it get's to anywhere between 12-15% and stays put, with the dots flashing as if it's loading...but not. If I switch Preview on - the preview shows up just fine, however, bucket do not appear and the render is not finished.

I have split the scene up using multiple render nodes, each render node to handle groups of objects. By doing this i've seen that the issue is caused by the only object with a displacement map in the scene. the object is 2,670 polygons and set to catmull-clark subdiv level 4...It's not that heavy. Would it be that I am asking too much by asking for a displaced object and everything else in the scene to be a forced matte? My render time is a bit through the roof - even with the scene separated this way. I have 6 lights in the scene including an HDRI. lights set to sample level 4. My camera AA is at 7 everything else at 5. My machine has a threadripper 2590x (16 core) and 64GB DDr4

[lee_griggs]

What does the log file say?