Working with the "work schedule" today and found that it refused to save, "try again later".
It defaults to 9am to 5pm. I work 8 till 4. I ran down the lists, clicking, tapping a number, changing 9s to 8s and 5s to 4s. It changed the 5s to 4s but didn't preserve the PM. I finally realised that it wasn't saving because my start time was later than my finish time.
Input validation is clearly checking that the start time is before the end time but it's not alerting the user to that. The "Unable to save. Try again later" is not just unhelpful but misleading. Trying again later won't help!