outbound SMS sometimes goes to wrong phone #

In the AirDroid v1.1.0 beta web interface, I went to messages and opened an existing SMS convo thread. I then typed and sent a new msg in that same thread in the web interface. The message ended up being sent to a different phone number of the same contact. When looking in the phone's SMS convo app, the sent msg actually shows in the original thread as if it was sent to that thread's phone # even though it went to a diff phone #.
I'm using stock Android 4.2.2 on a Galaxy Nexus (takju)