Mine has been doing this for months. I disabled test participation. I deleted and reinstalled the app. Nothing.
THEN, I read where after you delete the app, turn the device OFF before reinstalling app. Once I did this, I have not had a crash since.
So. Delete app. Power off device. Power on device. Reinstall app.
Check that the ROKU cannot alter the refresh rate of the TV. It's somewhere in the settings display menu. That fixed it for me. Stable ever since.