"When this robot destroys an enemy robot, return that robot to your hand. " Break the game

[Zergla]

When a robot with attack another robot, it doesn't destroy it, letting it at 0 or minus something hp, until something happen (like the player selecting a card).
At this point, both the destroyed robot and the attacking robot get removed from the board, as excepted.
Then the active player will get back the robot card. This always happens despite the 7 card limit (I believe it to not generally by the case).
Then the player can't place any card, nor move any robot, nor end their turn, making the game impossible to continue.