Review round 1 (issue 1126 note 72): the inflight check, the watch and the look were three locks, so a second request or the builder's own look could build the key twice; the answer said asked when the look wrote nothing or the build failed before its asks.
The builder retakes a failed key only when it looks at its module again, which nothing does for an unchanged module. The tool makes it look now, with the claim's own rules, and refuses a key that is done or waiting.