Issues with iMessage when switching data carrier (wifi <|> cellular)

[DaBigDogg]

So I have had this issue with my 5S and now my 6+ in iMessage. Not *always* but I've run into issues sending messages via iMessage when I associate with wifi in that they don't send. I'll get an error message saying "not delivered" and it will stack as many outgoing messages I try to send. However, if I force the first message to send as text, subsequent messages will go through afterwards without issue. If I go from wifi to cellular I have no issues whatsoever and when I have these issues on wifi, my data works fine (incoming emails, Facebook notifications, etc.). I used to run cellular data only because I had unlimited but now I have a cap so I intend on using wifi when possible...but to have to send my first message as a text just so I can use iMessage is annoying...