I ran into an issue where converting a heightfield to a polygon mesh using the Heightfield Convert SOP leaves values in the uv.z component. This ends up causing baking errors and artifacts when you try to bake down the heightfield in COPs. You can easily fix it by dropping down a wrangle to set uv.z to 0, but it's pretty unclear why it happens and took me quite a while to figure out! I have added an example file.

Hi there!
Yeah, this has been reported in other situations where some UV based SOPs output UV.z values.
There is a toggle on Rasterize Setup and Bake Geometry Textures for 'Remove UV Z Values', this toggle is ON by default in Houdini 22, but off by default in H21, as to not break backwards compatibility.
This should help with your bakes which have UV Z values.

Hope this helps!

thanks a lot!