You can find more information on the blog.

If you didn't restart Remote Buddy after the update, you might have 
two entries for Plex. Usually, this is not necessary, but this is a 
special case, where a scripted Behaviour (created with the Behaviour 
Construction Kit) is replaced by a native Behaviour (written in 
Objective-C, compiled in Xcode).

Regarding "Plex II": this is not part of Remote Buddy. If you 
installed or created it yourself, you'll find it at

~/Library/Application Support/Remote Buddy/Behaviours/

(Re)moving it from there and restarting Remote Buddy should do the 
trick.

Best regards, 
Felix Schwarz