So each time I run "bin/celerity map" it updates the Celerity maps in all of the modules. Unfortunately the behaviour of the "requires" section is incorrect, because for external modules bin/celerity map will add things like "javelin-behavior" into that section. When Phabricator attempts to resolve the requires, it can't find "javelin-behavior" in the external module (because it exists in "phabricator") and hence causes pages not to load.
The correct behaviour is that Celerity should check and resolve "requires" across modules.