Whether using Yaata or Messages, I have been typing text messages throughout the day and to begin with, the app is very fragile, cursor moving around, screen flickering, etc.
But now it's tying messages on its own.
So I shut it down and restart, and it's quiet for a bit and then acts up the same way again.
Turn off word suggestions and see if it does the same thing. If not, then the keyboard is sensing movement when there is none. And if so, do your fingers get really sweaty or oily?