Quick test (with a different zone + modifying strings in the binary) suggests the name of the .wld fragment mentioned in my last post does not matter.
You did rename "highpass.wld" to "highpasshold.wld" and "highpass_obj.wld" to "highpasshold_obj.wld" inside the renamed highpasshold.s3d and highpasshold_obj.s3d, using
S3DSpy or
EQGExport, yes? I feel like people were running into problems even after doing that though, iirc...