Update File - Repo files REST API is throwing error which is not documented

I’m getting this error message for update file REST API documented under Repo files.
What does this error message mean? It’s transient and unable to reproduce, file name is correct for which I’m updating.

9:reference update: reference does not point to expected object.

In my case, the error was due to conflicting use of the HTTP client by concurrent (go) routines.