I'm curious as to which key it is that you hear that noise from, i.e. whether it was the same one I noticed it on. I only noticed it when one key was depressed as well (I call it the F key; index finger of right hand) and it just sounded like a hard slap when there wasn't really one (or a cross between a slap and a sticky pad). But then again I tried another all-straub flute and didn't notice a peep. So I'm not really sure what the deal is; sounds like sometimes it's there and sometimes not. Something that probably bears noting, too, is that when I tried that flute w/ the clicking Straub on it, my two listeners I had in the room with me said they probably wouldn't have noticed it had I not pointed it out. That makes me think that an audience may be unlikely to notice anything.
But what matters most is that you're happy with what you got, and I'm sure there are zillions of other features on your new flute that outweigh that slight inconvenience if/when it happens.
One more thing -- I'm certainly no tech, but it's never a good idea to pull out pad drying paper while the key is still depressed whether it's a Straub or regular felt pad (even though I've heard Straubs are more delicate in that respect than felts). Simply put the paper in, press key down, release, and remove paper. Pulling the paper out while the key is depressed, I've always been told, will risk hurting any type of pad. Someone with more tech experience please correct me if I'm wrong on that.
BTW, I got my newly overhauled flute back over the weekend. Plays beautifully. I did traditional felt pads, but I will re-evaluate Straubs next time. That was it's 40th birthday present (my flute was made in 1967); its owner turns ____ in a few days

SK