What should I do if I flash back when sending a text message?

Settings-Application Manager-All Information-Clear Data

Settings-Application Manager-All-Phone Book-Clear Data

Try to restore the factory settings after the important data of the mobile phone is backed up: Settings-Reset-Restore the factory settings.

If the problem still exists after the above operation, it may be a system or hardware problem, and it needs to be repaired in a professional repair shop.