If you are holding a minion during your opponents turn and they play dirty rat and try to pull that minion, the minion will never leave the board however you will be able to fill your board with 7 minions (not counting the one that’s pulled from the rat)
This is not generally the case.
Can you be more specific? Which minion was is that was pulled from the hand? Do you have a replay?
That’s how dirty rat is always played.
Nobody else is complaining about this bug, so it must have been caused by some specific situation in your game.
Can you share the details?
What minion was pulled by dirty rat?
How did it die?
What were the other seven minions?
Were they played normally, or were they summoned by a spell?
etc etc etc.
I think they mean that, while it’s your opponent’s turn, and you manually hold the card while waiting, and the minion you’re manually holding gets pulled onto the board, then it triggers the bug of it visually not leaving the board once it dies

you manually hold the card while waiting
What does “manually hold” mean?
You can’t actually move the card out of your hand, can you?
Do you mean hovering the mouse over the card?
You can pick up a card and drag it on your screen, as if you were about to play it.
During your opponent’s turn the card will not be allowed to go further than your hero portrait, you can’t hover the board with it
But you can still select a card and hold it with your cursor while waiting for your turn to start
This has no gameplay impact but could be related to a visual bug, for example if the game was still remembering that you are holding that card, because it couldn’t properly end the “currently holding a card” animation because of the card leaving your hand without you releasing it, making the card still appear to you because the game thinks it’s still in your hand somehow