Difficulty removing info from metadata presets

I am importing RAW photos into Lightroom 6. I have several Lightroom presets that I have created. But there is a phrase that appears in the "Camera Info/User Comment" field when the "Custom" metadata preset is selected. No matter what I do, I have been unable to remove that comment. I have another preset without that comment and when I try and apply that metadata info, it does not overwrite what is written in the "custom" data. I have tried everything I can think of - gone to Preferences and Show Lightroom Presets Folder and deleted the "custom" file as that is the one that has the comment. Every time I try and import a file, even if I do not apply a metadata preset on import, the custom import fields end up tagging into the photo. Whenever I think I remove it, the comment reappears when I open the Edit Metadata box again. Any one have any insight on deleted the "custom" tab or resaving? I tried blanking out the field and doing a "save as" and it doesn't work.

Thanks.