The view with the 0s and -5 is showing the change in pressure since the last observation (so 3 tires haven't changed but the passenger rear has dropped 5 PSI). It's not some kind of "broken sensor that's showing 5 PSI of vacuum".
A negative # isn't a "negative tire pressure" reading but rather indicates the amount of change since the last reading (e.g. it thinks you've lost 3 PSI).
Canadian vehicles purchased new include a "no export for 1 year" clause in the sale agreement. The dealer says that Porsche will disallow warranty claims for the vehicle if made in another country during that period.