FAQ they'll ask anyway...

» Error Couldn't determine your position :/ Is your head in water?

If you get this error despite your head being in pure air make sure to set the gamerule logAdminCommands to true:

/gamerule logAdminCommands true
!raw /gamerule logAdminCommands true

» Some commands react really slowly

If only some commands react slowly (such as !muuhhh or !whois) then you've probably running a version of ruby which is affected by some sort of thread synchronization slowdown. Try upgrading to a newer version of ruby (downgrading may also work if upgrading isn't an option). Known ruby versions (mind patchlevels) which seems to be affected: