HTC One M9 :: Group Texting On Phone - Converting To MMS Message

I recently bought an M9 and have been loving most of the features. I've used a WindowsPhone for the past ~3 years and wanted something different. For years now, I've been a part of a group text with a few friends. There were no issues with it on my old phone, but I'm running into some issues with the M9.

For example: When I open the group text, there's a bubble that says "Converting to MMS message" every time. This happens even if I just backed out of the message and re-entered it.

Every time I send a message, a loading icon pops up in the middle of the screen. After the loading icon goes away, the message that I sent has another icon inside of it that stays there for a few seconds. Eventually, that icon goes away too. Some of the messages that are sent to me by my friends come through as individual texts with a download link. If I follow the download link, it appears in the group text.

Scrolling through the group message is extremely choppy. Everything else on this phone has been smooth, this is the only thing I've noticed that doesn't load well