It's happened a few times now that I restart Houdini, cook a HDA processor but it doesn't seem to update correctly. Dirtying and recooking seems to keep the old output in it. If I destroy the old hda processor and add a identical new hdaprocessor to replace it then it works.

This happens every time I restart houdini or it crashes.

So in the image below you can see what's happening, the first image is from the upstream node where the terrain is flattened. the next node after that however doesn't read the input correctly. Only when creating a new hda processor that's exactly the same as the second one it works again.

I would check your “Cache Mode” setting on HDA Processor. If it's set to ‘Automatic’, it will look for its output file on disk and if it already exists, the work item will be marked as cooked (therefore skipping the job execution).

Are you able to attach a .hip file?