What was going on
After updating flyctl to v0.1.52, fly deploy started hanging 5-10% of the time. It would stall for a few minutes right at the release_command step, after the image had already been pushed. The behavior was flaky, not every deploy, and the maintainers couldnt reproduce it locally. They reverted the suspected change and closed the issue in July 2023.
What fixed it
A change in v0.1.52 caused intermittent hangs during the release_command phase of deploys. The fix is to upgrade to v0.1.53, where the change was reverted. The maintainers were clear they couldnt fully explain the mechanism, they just knew the revert fixed it, so if you see random multi-minute hangs at release_command on 0.1.52, bump the version.