While right clicking beacon with terrasteal.
FML Crash log: http://pastebin.com/4zFDWjJC
Edit: You used @SideOnly. Forge guys advice people not to use it as it was created for forge internals.
Event thought you annotated static field with it, static constructor stays the same throwing NSFE.

It is server. Look at my edit

Yes, client side fields being worked on server.

Hm, client side issues, I'll have a look.