This is a guess, but probably worth a try. I assume that you are using teflon tape on the threads? Consider putting another wrap or two on there. There will be a limit on how much you can use before it won't be able to be started into the fitting, but as long as you get it started and enough turns, it doesn't have to go to the "bottom" of the threads. To help hold things in alignment, consider also using some pipe dope. Once this stuff dries, it helps keep the faucet from loosening. The faucet doesn't need to be tightend until it bottoms out, it needs maybe a couple of turns past where you can hand tighten it. More won't hurt. You know you've reached the limit when you split the female part , but you don't want to go there!