I am in the Beta also but I haven't encountered this problem. You could try clearing the system cache and see if that works. Also I don't think you can get out off the beta, However if you leak Beta content Microsoft will kick you out but you may also get banned from Xbox live and legal action may be taken.

you could try re downloading the beta update if you think this may be the problem by going to Settings > System > Storage > Highlight your primary storage device > Press LB, RB, X, LB, RB, X > Yes. But otherwise i say just do these steps to make sure before having to revert dashboard.

Make sure to delete profile only.

Delete Xbox LIVE profile safely
Before you delete your profile, make sure your know the password and username for your Microsoft account that is associated with your profile.


Go to Settings, and then select System.
Select Storage.
Select All Devices.
Select Gamer Profiles.
Select the gamertag that you want to delete.
Select Delete.
Select Delete Profile Only. This deletes the profile but leaves saved games and achievements.


Clear Xbox system cache


Press the Guide button on your controller, go to Settings, and select System Settings.
Select Storage or Memory.
Highlight any storage device, and then press Y on your controller.
Select Clear System Cache.
Clear your Xbox system cache 3 times in row.


Restart your console.

Download Xbox LIVE profile.

Press the Xbox Guide button on your controller (large X button in the center of your controller).
Select Download Profile.
Enter the Microsoft account associated with your Xbox LIVE gamertag.
Enter your Microsoft account password.