I have had this same issue on my Bionic (rooted stock) for the past couple of months. It seems to have mostly started at the same time I tried using Green Power battery saver. I finally deinstalled Green Power and the issue with GV is virtually gone, although it will still seem to stumble, or at least take a bit for a message to complete sending sometimes. The issue NEVER happened using the GV web client.
Here's a couple things I've noticed:
Sending the first message in the morning from the phone, using a current conversation, would usually cause the worst problem. Seemed GV would get hung as it tried to reconcile making the new thread for that recipient. Letting it time out and then press "refresh" would usually work, but result in the recipient getting a double text.
If I REALLY wanted to keep a single conversation thread going with a certain user, I'd make sure that the first text I sent each morning was done from the web client. For some reason that would go thru fine AND keep the previous day's thread ongoing.
As I spoke to my recipients, it seems that the original text actually DID go thru, but the phone app never got the completion signal. Therefore when I'd hit refresh the app would send a duplicate of the "failed" text.
I'll sure be glad when some of this hangout-voice-talk-chat-G+message-Gmail business is sorted and either combined or properly integrated.
