Text messaging so slow it is nearly unusable

I have a Galaxy S5 running 4.4.2. I am trying to send a text message to a certain contact. When I select their name from the list of messages, there is a 30 second delay. While typing, sometimes there will be a 10-15 second delay for each letter. If they send me a message while I'm trying to type, there will be a 30-60 second delay. Texting this person is so slow it is almost unusable. Other contacts are slow as well, but still usable. This is with no other apps running. My guess is that this could be caused by the lengthy text message history for this particular contact, but I doubt this is the case for the following reason: It seems extremely unlikely that I should be unable to store and display several megs of text on hardware made in 2014. I want to preserve this text history in any case, but I don't necessarily need to display it all on the screen at once. Thanks! Edit: I have tried clearing the cache, no effect.