I have a galaxy s5 and every time when i have a MMS group chat with iphones their messages are always delayed and when i send a message to my friends in the group chat, half the time they never receive it. I also use a texting app called Textra but it always says check APN setting>MMS proxy port but my proxy port is on 8 and it still says that and like i said its 50/50 if i'm able to get their messages on time. I tried using my default messaging app but that's even worse. Is it because androids are not compatible with having group chats with Iphones? Or is it an apple problem?