iMessage not working with wifi calling
When using wifi calling, iMessages won't send. They will try, then fail, then revert to text messages.
I'm using an iPhone 5S, up-to-date iOS 8, and T-Mobile. I have the option enabled to send as text if iMessage fails. My office is below ground level so cell signal is weak and cuts out, hence I use wifi calling. iMessages send perfectly when I'm not at work (I think it even works in similarly weak cell signal above ground when I'm using wifi calling).
I believe this bug hurts battery (at the very least, it tries to send the iMessage for 30 seconds before alerting me that the message failed (turns on screen and alert), only to successfully send it as an SMS afterward), besides annoyances such as delayed sending of messages.
iPhone 5s, iOS 8.4.1