Not sure what's going on but for some reason my heightfields are incompatible with a bunch of SOPs. This happened all of a sudden while I was working. Opening new scenes or restarting does nothing.
Using Houdini FX 18.0.532
For example using just the hill from the terrain fx shelf produces this:
The error on the slump is this:
The mask by feature node also only ever shows the same mask no matter what the settings are at: