Hey @dvr welcome to the Community! 👋

The Square Point of Sale app can log out if there is an iOS update, or if there is an app update. It can also log out if the owner/account holder has updated any security details (such as the login password, or employee permissions/passcodes). 

If you're seeing the log-out happening randomly with no patterns, I would suggest deleting and reinstalling the Square Point of Sale app. You will need to sign in and enable permissions again when your app has reinstalled successfully.

Hopefully this information is helpful, let me know how you get on!