FAQ: What does Auto-Import do with duplicate contacts or leads?

When you connect a Salesforce report to a Flow for Auto-Import, Groove will not import the same Lead or Contact twice. However, reps can manually override duplicates if necessary by manually re-importing a Lead or Contact. 

If you want to prevent users from importing the same person to multiple Flows at the same time, you can enable the Flow Safety Setting to prevent users from adding someone to a Flow if they are already active in another Flow at your organization.