I've had my share of problems with Viber in the past, but overall it's a very good, very solid app. There are bugs sometimes, but they are always fixed. At the moment (been happening for weeks) I can't easily send any media files. Just gets stuck at 0%, and eventually it remains unsent. Killing the app and restarting it fixes the problem temporarily - ONE file is sent, but the same thing happens for the next one. Same on wifi or cellular. Annoying, but I'm certain it will be fixed eventually.