Duplicates and how to manage

Hi, new to Tessitura as of December last year, though not new to databases.

We have a huge amount of duplicates, which seem to mostly be the result of donors logging in to buy tickets and setting up new records for themselves. Today I came across a record of a man who apparently has four daughters named Ruby! Each time new tickets (for classes in this case) have been booked, a new record is set up.

I know how to merge duplicates. My question is more around best practice in catching these and fixing as they come up, and also if anyone can shed any light as to why this happens and if we can do anything from the ticketing side to prevent it??

Any thoughts gratefully received.