Microsoft.TeamFoundation.Git.Server.GitObjectDoesNotExistException when creating Pull Requests

[Patrick-3000]

We were using Dependabot for MS Azure Devops V1 but as this version got deprecated, we switched to V2.

However, Dependabot is not able to create Pull Requests as it fails with

Creating pull request '[npm-Updates]: Bump lru-cache from 11.0.0 to 11.0.1'...
 - Pushing 1 file change(s) to branch 'dependabot/npm_and_yarn/main/lru-cache-11.0.1'...
🌎 🠊 [POST] [https://***/***/***/_apis/git/repositories/***/pushes?api-version=5.0](https://%2A%2A%2A/***/***/_apis/git/repositories/***/pushes?api-version=5.0)
🌎 🠈 [500] Internal Server Error
{"$id":"1","innerException":null,"message":"TF401035: The object '450425a1a469b12373a3e49b8bd23bfca51a11e3' does not exist.","typeName":"Microsoft.TeamFoundation.Git.Server.GitObjectDoesNotExistException, Microsoft.TeamFoundation.Git.Server","typeKey":"GitObjectDoesNotExistException","errorCode":0,"eventId":3000}
##[error]Failed to create pull request: Error: Request to '[https://***/***/***/_apis/git/repositories/***/pushes?api-version=5.0'](https://%2A%2A%2A/***/***/_apis/git/repositories/***/pushes?api-version=5.0%27) failed: 500 Internal Server Error
Error: Request to '[https://***/***/***/_apis/git/repositories/***/pushes?api-version=5.0'](https://%2A%2A%2A/***/***/_apis/git/repositories/***/pushes?api-version=5.0%27) failed: 500 Internal Server Error
    at AzureDevOpsWebApiClient.restApiRequest (/home/vsts/work/_tasks/dependabot_d98b873d-cf18-41eb-8ff5-234f14697896/2.37.1025/utils/azure-devops/AzureDevOpsWebApiClient.js:551:23)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async AzureDevOpsWebApiClient.restApiPost (/home/vsts/work/_tasks/dependabot_d98b873d-cf18-41eb-8ff5-234f14697896/2.37.1025/utils/azure-devops/AzureDevOpsWebApiClient.js:528:16)
    at async AzureDevOpsWebApiClient.createPullRequest (/home/vsts/work/_tasks/dependabot_d98b873d-cf18-41eb-8ff5-234f14697896/2.37.1025/utils/azure-devops/AzureDevOpsWebApiClient.js:177:26)
    at async DependabotOutputProcessor.process (/home/vsts/work/_tasks/dependabot_d98b873d-cf18-41eb-8ff5-234f14697896/2.37.1025/utils/dependabot-cli/DependabotOutputProcessor.js:81:42)
    at async DependabotCli.update (/home/vsts/work/_tasks/dependabot_d98b873d-cf18-41eb-8ff5-234f14697896/2.37.1025/utils/dependabot-cli/DependabotCli.js:116:55)
    at async run (/home/vsts/work/_tasks/dependabot_d98b873d-cf18-41eb-8ff5-234f14697896/2.37.1025/index.js:82:57)

For me this looks like a bug (especially considering that with V1 we could create PRs), but maybe anybody has a suggestion of what I could try as I am out of ideas...

[Patrick-3000]

Closed due to duplicate with #1413