Do you have a valid 2.0 config file in all branches? It’s possible that for the next 15 days or so, until 1.0 ceases you’ll get 1.0 builds occurring for all those other branches. When I first started using CircleCI I pushed a branch that had a 2.0 config file after following the project repo, then after that all other branches started to build on commits being pushed. I contacted support and was advised that this would occur as the other branches will run as a 1.0 build if it can’t find a 2.0 config. So, your issue maybe related to that, also possibly check out the ‘Advanced Settings’ under Build Settings after clicking the cog/gear next to your project name. From there make sure the items around building on pull requests is set as per your requirements.
Also, if you can drop in your full config, it will help.
Also, based on what you’ve said here, I’d also be wanting to confirm the filtering in all the workflow sections you’ve defined for each branch. As branch filtering can be applied in a few different places as well as workflows, it’ll be easier to confirm if that’s a possible cause of the issue with a complete picture of the config if you can provide it.