Thank you for your question, we’d be happy to help you resolve this matter. By design, the Top Bar Hive body should only be accessible to bees by way of the entrance holes on the Entrance Board side. Unless alterations have been made to the follower boards, or the bar spacing is too far apart (the bars should be racked together), the only way bees should be entering the hive body is through the entrance holes. Also, depending on your micro climate, you may consider reducing the size of the entrance hole to reduce the risk of robber bees and yellow jackets from entering the hive.
Bees do often crawl up and around the cavity space located between the top bars and the lid, and while this is normal behavior, they should not be able to access the body of the beehive. If you still feel that bees are entering the hive body from between the bars, feel free to email us a few pictures of your hive with the lid open and we’ll be happy to take a look. You can reach us at the following email: firstname.lastname@example.org. We look forward to solving your potential issue.