Just bought Nokia Lumia 521. No issues at all when a text is sent to 1 other person, however when text messages are sent to more then 1 person either by selecting multiple contacts individually from my contact list or when I use the group text option inevitably one of the recipients in the group state that they received a blank text message or an "empty bubble" from me. It is driving me nuts because we often text in a group and like to see all parties responses contained in the same thread but my replies don't seem to make it to all people in the group....it gets to 2 of the 5 or sometimes 3 of the 5 but ALWAYS I hear back from at least 1 of the 5 people that all they received from me was a blank text......is this a known issue?