Apparently your mod depends on Shadowfacts' Forgelin, because when I downgraded from their brand new release (1.7.1) to the previous release (1.6.0). The error stopped happening. If it is dependency can you add that to your overview?
If it is not a dependency then there is an issue between the two mods.
Notes: on startup while looking for client side classes
crash report: https://gist.github.com/c2618bcae20e0180cfba96f0b7dec6d0
fml server latest: https://gist.github.com/f6a4c43bf22ebbca59504bf75a6a4083
Apparently your mod depends on Shadowfacts' Forgelin, because when I downgraded from their brand new release (1.7.1) to the previous release (1.6.0). The error stopped happening. If it is dependency can you add that to your overview?
If it is not a dependency then there is an issue between the two mods.