How to Export Text Messages

I need to export all SMS messages from one specific contact. I have tried going into the messages app and scrolling through my text messages but only get to a certain date and it crashes. I have deleted all unnecessary messages, rebooted my phone, ensured all updates are current. I have a backup on iCloud but cannot access the data in any usable format.

I'm happy to use screen shots, if I could scroll back without the app crashing, but would prefer another method to export the entire message history for that contact.

How can I retrieve my old messages? How can I avoid the messages app from crashing?