we kept having to shoot - Hemos tenido que seguir filmando
Lo peor de todo era que nosotros hemos tenido que seguir filmando una escena repetidas veces
We kept doing something = We continued doing something - that's the meaning
So, we kept shooting a scene = We continued to shoot a scene
we kept having to shoot a scene = We continued to have to shoot a scene
we kept having to shoot a scene again and again = We continued to have to shoot a scene repeatedly