Hi
We found a bug with facets that have white spaces. It doesn't happen when you clear the facet at the first time but if you navigate to a product detail page and then return to the product list and clear the facet, you will see the URL encoding white spaces differently to a "%2B" which represents a "+".
Here's a screencast to help with repro: https://www.screencast.com/t/BsvkZHLw3L56