Found what I think was a bug and was wondering if someone with a Nexus 5 and an iPhone could confirm. Take a picture with the Nexus 5 and send it as a MMS using Hangouts to the iPhone. Then with the iPhone, send two pictures in one MMS to the Nexus 5. When you attempt to open either of the two iPhone pictures on the Nexus 5 the screen will briefly show the picture you tapped on and then flicker and show the picture you had originally sent to the iPhone. This only occurs if the iPhone sends two pictures in one MMS, if the pictures are sent separately the problem doesn't occur.