If you try to branch from a commit whose message starts with square brackets containing two words split with a forward slash, such as

[Blah/fix] Some commit message

And then you try to create a local branch from that commit, SourceTree misinterprets the text as a remote branch name and thinks the local branch tracks it. When it then refreshes the view, it produces "error 128" messages because there is no remote branch with that name.

To reproduce, create a clean Git repo. Make a first commit. Then make another with the message

[Blah/fix] Some commit message

Then use SourceTree to branch from this point. Now switch back to master, and right click the new branch. Notice that SourceTree has populated the "push to" items because it thinks there is a remote branch involved. Now choose to delete the branch, and note the "delete remote branch" option is available when it shouldn't be.

This causes huge problems when trying to branch in a repo that does actually have a remote and someone has made a commit using that brackets syntax.