I had similar troubles plus a lot more with Looby on the lunge, you just have to stick at it. I found this video recently that I thought was useful so sharing
I know theres always dispute on using baler string but I always do that too and my farrier here in the US wont have a horse tied unless its got something that will break if the horse does panic. I think maybe people have never seen what can go horrifically wrong - doors pulled off and horses bolting dragging them behind, bricks pulled out of walls and hitting horse or person on the head, fences pulled out, headcollars ripped into flesh
Each to their own thing of course but I'll stick to my way I think!!!