They’ll likely ignore your ticket, but you should try.
Check if a Long Shadow option exists (did on landscapes)
Make sure that the material is flagged to receive shadows for the heightfield mesh.
The short shadow up top looks pretty good - are you sure that reflection/light bounces aren’t what is causing rhe shadow change?
Either way it does look like a shadow lenght issue… cycle the 2 images quick enough and you notice that the direct shadow is perfectly the same…