It is commonly the case with our supporters (particularly older folk) that partners/family in a household will share the same email address. The other case is when a coordinator uses their email address for a person that doesn't have one. When this same email address is used for successive sign-ups on rosters, then the first person's name and details are overwritten with the details of the subsequent person. This causes confusion on shift rosters and events regarding who is actually signed up, as their distinct rosters are then merged together.