Corrupted iPhone Backup

My mom's iphone13 battery decided to commit suicide. so we went to change it at Apple. they said you have to backup your phone as we might format it. So i confidently backed up the phone using iTunes. When we got the phone back I tried to restore it, waited more than one hour for the restoration process. THEN the iPhone is not restored at all. I went to a mobile repair shop they said sadly cant be restored as the backup is corrupted. So any of you guys had this problem before and got it fixed?!