We have a maven job Foo with 10 downstream dependencies. In the Job page all the dependencies are noted clearly as well as on the the actual build page. Hower some of the downstream Jobs show with "(none)" instead of their build number and the log of the Foo build shows the "Triggering a new build of xxxx" lines, but only for 7 out of the 10 that should be triggered.
Jenkins clearly knows about the SNAPSHOT dependency and shows the downstream relationship correctly, yet it 'forgets' to trigger some of the jobs.
Confirmed with 1.550 and 1.551.