Thank you for taking the time to report this issue to Unity.
We have reviewed your report carefully. Because this issue is highly inconsistent and difficult to reproduce, and it no longer occurs in the latest version of the Unity Editor, we will be closing this ticket as "Won't Fix" / "Cannot Reproduce."
We recommend upgrading to the latest Editor version to see if that resolves the problem for your project. If you encounter this issue again in a newer version, or if you discover reliable steps to reproduce it, please feel free to let us know or open a new bug report so we can investigate further.
Thank you again for helping us improve Unity!