Exactly the same here. SportNav Auto 2013. Just before the car's 3rd birthday I was getting invalid TPMS faults randomly every ~30 miles. Car had Bridgestone tyres on the front and 1 Bridgestone and 1 newer Continental Sport 5 XL on rear(an emergency replacement after a puncture in France ~ incidentally we had to drive back to the UK in a hire car to pick up that tyre as there were no suitable tyres in Northern France!). I took it to Mazda dealership 3 times. After the 3rd visit, despite them saying that they had done nothing, the problem seemed to go away... until 2 new Continental Sport 5 XL tyres were fitted to the front. Ever since I've been getting false "Check Tyre Pressure" warnings every 30 or so miles unless, bizarrely, I've let the tyre pressures drop a bit. I've had the car thoroughly checked by a Kwik Fit Brake specialist who can see nothing wrong and suggested returning to the Mazda dealership. *sigh*