I came back from vacation to find that about 20 columns, with headers but no data, have mysteriously added themselves to my Smartsheet. I created this version by using an older sheet as a template 3 years ago and streamlined by deleting a lot of excessive information tracking columns. And I use some hidden columns, so these aren't those. Could they have added themselves back in somehow 3 years later? I'm planning to just delete them again, but I'd like to know what might have happened before I do that.