SealedHeroes
By default, the Hero Seal count is 4 which can be changed via the HeroSettings.ini located in the Server's Config Folder.
Once 4 is reached and manually deleting the sealed hero item from a player's bag. The seal count isn't reset. Once the limit is reached and the player only has 1 hero they can not seal the hero due to the cap.
I notice that this is different on your DB than on GamePotUSA (where i saw heroes originally) Sealing a hero was so you could sell it, otherwise to change hero you used the hero management window ( [@MANAGEHERO] NPC Command) and could swap hero through that and increasing the amount of Heroes you can have with Scroll (case 14 in code, missing ITEM from your DB, last I looked).
No idea if this is still how it should be or like official is currently though, just a thought i guess