/res locs looks like it should be a command according to the wiki, but if you try to do it then you get this:
That's most definitely a wiki bug and not so much an in-game bug. Going to fix this right now. Edit: and done. Thanks for mentioning this! Edit2: However... The /help res command also mentions this. I'm pretty sure that this command has likely become obsolete so I'll still point this out to the staff as well. Edit3: And contrib. team to the rescue (Thanks Penguin!). We also discovered that this thingie sneaked into the commands page as well and that has also been fixed. It'll be fully addressed soonish enough.
/res locs and /res loc are interchangeable. You'll get that same error message if you do /res loc with no arguments after it, too. (To Shell, which I realize is now redundant as I've already posted. :l)
It's only the /res loc and /res locs commands that don't work. /res loc set, /res loc list etc still works.
If I can add to this as the bugs /mobarena does not work on smp5 as non staff I believe do not have hte permission to use it only there.
/mobarena works on other servers because it's a bungee command; it's a redirect to /smp5. On smp5, however, /mobarena (and the /mba shortcut) are used by Staff members to run the mob arena - set winners, open doors, change round types, etc. The /mobarena command as a shortcut for /v mobarena was an oversight. When the development team realized the mistake, it was quickly fixed.