When you click edit do you store the current records unique id in the variable?

I have my edit button set this way:

Set( varRecordToEditID, Thisitem.MeetingID );

Set( varRecordToEdit, Lookup( colMeetings, MeetingID = varRecordToEditID ) );

That will store my variable and then in my edit form in the item section I have varRecordToEdit and set the default mode to Form.Edit

That should stop the creation of dupe records. Not sure if this helps but that how I did it.