You have <If some trade exists> on every tick. This will not create pending orders by itself, because there is no trade initially. But even if you have some trade, it will start creating unlimited number of pending orders, because the trade is running and on every tick you create a new pending order.
So what you have is an endless loop which (fortunately) cannot start, but if it ever starts...
Try it in the opposite way, with "No whatever exists". In this way you create trade/order when it does not exists. And then, after it is created successfully - it will not pass the "No..." check again.
Also you can check the number of trades/orders if something like this is needed. "No..." is checking if 1 exists.
There is also "on Trade" event, but if you can do everything under "on Tick" it will be better. Because the Trade event is fired ONCE when something happen, while "No..." block is basically a condition that does not depend on events.