require.config vs define() for custom modules with dependencies

We've run into an issue where we have a custom module that has momentjs and are trying to use this custom module in another module. If we try to include this using require.config with a relative path to the custom module, it does not allow it (says it cannot find the module). If we take out the reference to momentjs so the define is something like define([], function({...}); then it'll work fine. However, if we keep momentjs as a dependency and do NOT use require.config and just use a relative path within the define array, it works just fine. My