Q: Screen blanking out rotating 90 degrees while texting

Hello beau-tech,

If I understand correctly, the Messages app isn't behaving normally when you're sending text messages. The easiest way to resolve unusual intermittent issues with apps is to restart the app or the device as shown in the article below.

If an app you installed unexpectedly quits, stops responding, or won’t open - Apple Support

Restart the app

Close the app and open it again.

 

Restart your device

Turn your device off and back on.

If the issue persists, try restoring your iPhone 6 as described in this article:

Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support

Cheers.