Comment 12 for bug 125420

Usually, for archives that are written to by a single person, those are stale locks. This is why bzr tells you how long ago a lock was created: if it was created a day ago, it is almost certainly stale and safe to delete using "bzr break-lock".

Stale locks cannot be avoided when using the sftp transport, or any other filesystem-based transport. If your sftp connection is brutally interrupted, bzr does not have a chance to release the lock.

The bzr+ssh:// instead of sftp:// transport (supported today by Launchpad) should not have this problem: if the connection is interrupted, the server-side bzr process can still release the lock.