If the threads are different, possibly this could be the result of an euro style faucet on a domestic shank. Or vice versus. Possibly not. During the last ten years, there has been a lot of development on stainless faucets. Stainless is harder metal than brass and is less forgiving while machining. The tolerances must be kept close. Some of the original faucets manufactured may have been off slightly and therefore may not fit or pour properly. If you know who manufactured the faucet, contact them or the vendor on your problem. Hopefully they can rectify your problem with a replacement.
Stainless by far is a much better product than brass as to beer contact. It is not bio friendly and stays cleaner longer. When dirty, it cleans rapidly.
Scott Zuhse, Instructor
Micro Matic Dispense Institute