我正在尝试使用VSTS NET6库编辑一个文件（gitItem）。我总是得到以下错误。

Microsoft.VisualStudio.Services.Common.VssServiceException: TF401028: The reference 'refs/heads/workbench' has already been updated by another client, so you cannot update it. Please try again.

不管我是否创建和使用其他分支，错误都是一样的。这是我的例程代码。我相信我遗漏了一些东西，但真的不知道可能是什么。
主方法是SaveConfigurationFileRepository。我首先获取要编辑的项，以确保它存在并获取其objectId。我使用changeType = edit，因为我想更新现有项的内容。如果代码太长，请原谅。

using Microsoft.Extensions.Configuration;
using Microsoft.TeamFoundation.SourceControl.WebApi;
using Microsoft.VisualStudio.Services.Common;
using Microsoft.VisualStudio.Services.WebApi;

namespace ConfigurationManager.API.Infrastructure.FileSystem.Context
{
    public class InfrastructureFileContext : IInfrastructureFileContext
    {
        public static FileContextConfiguration? contextConfiguration { get; private set; }

        public string Url { get; set; }
        public string ProjctName { get; set; }
        public string RepositoryName { get; set; }
        public string WorkingFolder { get; set; }

        public InfrastructureFileContext(IConfiguration configuration)
        {
            contextConfiguration = configuration.GetSection(FileContextConfiguration.SectionName).Get<FileContextConfiguration>();
        }

        public async Task<int> SaveConfigurationFileRepository(string groupName, string appName, string fileName, string fileContent)
        {
            // Create instance of VssConnection using Azure AD Credentials for Azure AD backed account
            VssConnection connection = new(new Uri(contextConfiguration?.Url), new VssBasicCredential("", contextConfiguration?.AppToken));

            // Get a GitHttpClient to talk to the Git endpoints
            using (GitHttpClient gitClient = connection.GetClient<GitHttpClient>())
            {
                // Get data about a specific repository
                var gitRepository = gitClient.GetRepositoryAsync(contextConfiguration?.ProjectName, contextConfiguration?.RepositoryName).Result;
                GitVersionDescriptor gitDes = new GitVersionDescriptor() { Version = "workbench" };

// Get Item to edit
                var gitItemToEdit = gitClient.GetItemAsync(gitRepository.Id, $"{groupName}/{appName}/{fileName}", versionDescriptor: gitDes, includeContent: true).Result;

                if (gitItemToEdit is not null)
                {
//Create commit objet
                    GitCommitRef newCommit = GetCommitForFile(gitItemToEdit, $"{groupName}/{appName}/{fileName}", fileContent);

//Create refUpdate using gitItem.ObjectId
                    GitRefUpdate refUpdate = new()
                    {
                        RepositoryId = gitRepository.Id,
                        Name = "refs/heads/workbench",
                        OldObjectId = gitItemToEdit.ObjectId
                    };

                    GitPush gitChangesToPush = new GitPush()
                    {
                        RefUpdates = new GitRefUpdate[] { refUpdate },
                        Commits = new GitCommitRef[] { newCommit }
                    };

                    var gitPush = await gitClient.CreatePushAsync(gitChangesToPush, gitRepository.Id);

                    return gitPush.PushId;
                }

            }

            return 0;
        }

        private GitCommitRef GetCommitForFile(GitItem gitItemToEdit, string fileName, string content)
        {
            //Generate Git Commit
            GitCommitRef newCommit = new GitCommitRef
            {
                Comment = "Update configuration template",
                Changes = new GitChange[]
                {
                    new GitChange
                    {
//Also have tried to use Item = gitItemToEdit
                        ChangeType = VersionControlChangeType.Edit,
                        Item = new GitItem { Path = $"{fileName}" },
                        NewContent = new ItemContent
                        {
                            Content = content,
                            ContentType = ItemContentType.RawText
                        }
                    }
                }
            };

            return newCommit;
        }

    }
}