The imessage text box disappears on my iPhone 7 Plus

When I am having a text message conversation, I will go to reply to a text I received and my imessage text box has disappeared leaving me no way to type a message. (In the case of the photo above, everything under the message "I forgot; we can go. I just spaced it." is missing)

The text box is also gone from every previous conversation I have had and if I click the button to start a new conversation, the text box is also gone. I can get the text box back by restarting my phone; however, I don't think I should have to be restarting my phone all of the time, especially since it's only 5 months old.