We're currently limiting our campaigns to 50% traffic, but had a couple of instances where they accidentally went back up to 100% when making other changes to the campaign. @TSkaff managed to figure out this is happening when using the "Filter banners" tool.

Steps to reproduce:

1. Have a campaign with "Limit traffic" enabled and set to less than 100%
2. Visit the admin page, enter something in the "Filter banners" input and click "Apply filter"
3. When the page reloads the Limit traffic checkbox is no longer ticked, and saving the form would result in removing the traffic limit.

The "Campaign type" dropdown is similarly set to "No type (always shown)"