For the sake of troubleshooting, I've done a fresh install of forge, and only using Luggage mod.
Mod File: luggage-1.4.1.jar
Failure message: Luggage (luggage) has failed to load correctly
java.lang.reflect.InvocationTargetException: null
Mod Version: 1.4.1
Mod Issue URL: NOT PROVIDED
Exception message: java.lang.NoSuchFieldError: ENTITIES
I'm sure this will work out when FML has a stable release.
Do feel free to just close this issue as it's more of a heads up that the FML beta seems to be bugging with luggage at the moment

yeah, this is because I still have yet to update the mod to newer forge versions. I'll go do that real fast

fixed in 1de2eb7, I'll have a curseforge build up shortly. appreciate the report!