Sentry-cli set-commit works with commit range but not with --auto

I have no problems adding commits to my releases with
sentry-cli set-commit [VERSION] --commit [REPO]@[from]..[to]
with from/to being the range of commits. Also works with HEAD as “to”
When I try adding commits with the --auto flag, the debug log shows finding the repository, also the head commit, but leaves previousCommit set to null in the logged JSON dictionary. Afterwards, no commit is added to the repository but the CLI also logs no error. A while later I get the “Unable to Fetch Commits” email.

Any idea what could be the problem? We use GitLab and an on-prem Sentry.