I had the same problem and I could resolve it by creating the repo again with a trailing ".git" in the Git repository URL.

For example, use this

https://gitlab.mycompany.com/my-project/my-repo.git

not this:

https://gitlab.mycompany.com/my-project/my-repo 

If you omit the ".git", you can create the repo and do simple operations like a checkout in Databricks but for the diff etc it is going to break with the "Another git operation is in progress" error.