Its not a fault, its taps and dies. You cannot drill holes without a bit and you cannot create a thread without a "tap"
Worked for me yesterday. I made a mess of the first attempt by trying to over screw the metal thread or "Tap" into the plastic and on close inspection there was no thread. I thought oh well thats it
But then I re heated it up again, screwed it in and cooled it off under a tap. Result perfect female thread to fit the angle adapter into. I guess its just a new procedure that you have to learn. It works and I will use it again. Good tip Jikwan