The error message "Logout Error Could not parse data to legacy JSON" is due to expiry of security token after a certain time. Better HR requires the mobile app to be re-login every 6 months or so. However it could be a bug and is quite common in iOS devices.
You can solve it by two ways
Uninstall/reinstall the app
Logout and relogin
We always advice you to do complete uninstall and reinstall.