bug with columns in page builder

Discovered a bug where if I create a 3 column block (like with a 25% 50% 25% layout) then add some content and then switch BACK to single column, retaining just the text from the 50% block, then this CSS is staying written into the page. Happened in another part of the page where I had two columns with a 25% 75% section as well. Only way to get a full column again is to create a totally new column and switch it to single column before adding any text.

@media screen and (min-width: 800px)
#intro.builder-text-columns-1 .builder-text-column-1 {
    width: 50%;
}