The same thing happened on my 6v6/Highlander/MGE server :O
But I applied a workaround for the RTV command. I disabled the umc-rockthevote plugin and I made a custom "rtv" vote with this plugin http://forums.alliedmods.net/showthread.php?t=235115
For the "map doesn't change, it just set it to nextmap" problem, I updated the plugin to 3.4.7 beta from this post and everything seems to work fine now. I don't checked it myself, but my admins have not reported the problem again.
I don't know if 3.4.7 fixed the rtv issue btw :c
Thanks! I will try that version as soon as I can; btw, do you have the custom vote config for that RTV, right now?