A couple of things to consider with these gaskets.
The original phenolic gaskets- crunchy brown ones, you can't (short of being a gorilla) over torque them and the actually need quite a bit of torque to seat properly. What normally happens is it gets off centered a bit and you damage it that way. The best way to install the nozzle is to assemble it upside down with the gasket installed, I like to tiny bit of silicone grease on it to help keep it in place. Then place it through the yoke and screw on the main body while keeping the nozzle upside down until it's finger tight. If you have already installed the main diaphragm (which I usually do) then also install the pin and pin pad before starting the assembly.
VDH also sells a nylon version of the gasket, its white. This one requires a LOT less torque to seal and you can very easily destroy it with too much torque. I trashed several before getting it right. On this one, snug it up good then test for leaks and if needed add a little more torque but go easy. I use the same assembly method as above.
The phenolic ones are harder to get in straight but are much more forgiving of over torque- not sure you actually can over torque them within reason- than the nylon ones. I prefer the phenolic ones in most instances.