So, Bastok is in first place, I'm leveling Ninja, so figured I'd buy some darts and use it to skill up throwing along the way. Instead of throwing animation, my character starts singing. Good thing is that the throw still goes through. I find it funny that I can sing a monster to death like this XD.

If this info helps...
I play as a female hume, happened in south gustaberg. Haven't taken it elsewhere to test it out yet, just figured I'd put this down when it happened. Kinda having fun with it but the singing stacking on each other gets annoying.

Not sure if this helps, but I was lvl'ing NIN this weekend & using a chakram to skillup Throwing in Buburimu, did not see any singing animations; just the regular throwing animations. So it would seem that the error you see is not server-wide.