Which part of "Preview" do you think is responsible for your NFC not working right? When I had my 950 on the AU I tried the wallet app just to see what the difference was between using my phone and using my card. It worked perfectly but I didn't see any advantage so I stopped using it. In all fairness I only used it for a couple of days, maybe a week.
Many members, myself included, state unequivocally that the 950s don't do well on the Insider Builds. The Idol didn't work well for me either on any other build except the AU.