Remote Branches to Pull Are Always Empty

When i try to pull via SourceTree from a remote repository remote branches are always empty at first. I can retrieve remote branches by pressing 'refresh'. But i have to do this every time i launch this dialog. Even if i close and immediately open it again. I've compared this with my other MacBook and a MacBook of my colleague. Both installed SourceTree, having (almost) the same git-config. They do not have this problem. I removed and reinstalled SourceTree (even deleting files under ~/Library/Application Support) and it didn't solve the problem. After pressing 'refresh' remote branches are available for this moment. I also can see a loading spinner icon in the drop down menu when i open the pull dialog but there are not any results. Only after manually refreshing them.

The only difference between this Mac I'm having this issue and my second one is that I installed a plain SourceTree app on this one while I had the AppStore version installed on the second one before.

The last update didn't fix this issue. The issue occurs in every repository every time. It doesn't occur on the other Macs where the same repositories are used.

If necessary I can provide further details.