it could very well be a weak battery. new cars have so many electronics and sensors with really low voltage needs, so a weak battery won’t be able to correctly supply voltage to everything consistently and it could cause major disruption throughout the car. have the battery and alternator load tested at like an auto parts store or something. if all is well it could be an issue with the switch, the control unit, or even the rear calipers with the motors that physically engage the parking brake. but with the slow cranks you mentioned a battery is most likely. i’ve seen cars with dying/old/worn out batteries cause some really strange issues or throw the most oddball codes that make no sense in relation to the data being read or the actual behavior of the car. i think i have seen some recalls/tsbs related to mazda and the rear calipers failing so look into that to see if it applies to your car.