Oh, I see. Mine has no problem going all the way down to make contact. As I described, the issue happens before it is fully screwed in.

If it has trouble going all the way in, I’d think that would indicate the O-ring needs lubrication, more so than the threads.

The threads and O-ring on mine were very slightly greased when I got it. Not much, but there was definitely something on there. I’ll have to check if we still have some automotive silicon grease lying around.