Several times a day, the app will freeze up in the middle of me trying to type a message to someone.  It generally hangs for 1 - 2 minutes, then it seems to catch up with what I had typed in while it was hung.  This caused the UI to be unusable during these episodes.

I'm often forced to loading the web app to complete the conversation I was in the middle of having.

Workaround:

• Use the web browser to conduct chat sessions.