TortoiseGit: Why is Revision Graph not outputting properly (?)?

Question

git

There is an svn repository, with the following structure:

/project1
    trunk
    tags
    branches
/project2
    trunk
    tags
    branches

After migrating the first project (/project1) to git (v1.7.4.1) using svn2git (v2.2.2), in the new repository, when viewing the Revision Graph in TortoiseGit, I observe:

At the same time, new branches created in this repository are displayed normally (see. higher). If you look at the graph through the "Show log" in TortoiseGit or in git itself, then everything looks fine:

So where is the problem - in the repository? Or is this a TortoiseGit bug?