I have just installed and started testing your Participants database (great plugin!) and am having issues I haven't been able to find discussed in other posts.
When I created a page with the [pdb_record] shortcode, I had already set up 13 fields I wanted to display using display columns in the manage database fields page. 13 fields showed up in order as expected, piece of cake. Later, I decided not to show 3 of those fields and reset them to 0 per your instructions expecting them to go away. I've also tried to use fields=" on that page to make them go away, yet they persist. I deleted that page and started over, still there. I imagine I could reload a backup and start from scratch, but is there a better way?