The symptoms in my 69 reg AE are exactly as described in this thread regarding intermittent spurious charging and phantom stop the car messages that magically disappear after a few stationary minutes with the engine switched off.
Mine went 1 stage further yesterday (posted a thread here Inexplicable Loss of Electrics whilst Driving Today (ND2)) where it inexplicably just stopped at a set of temporary traffic lights 130 miles into a journey(hence should have been fully charged) all electrical power gone …nothing could be operated. Ludicrously simply operating the bonnet release catch in the car restored the electrical supply
Very disappointing that a common thread or pattern seems to be there on circa 2019 ND cars with this DC to DC converter especially with the sums mentioned. Mazda should be stumping up for this OR at worst offer the fix at a hefty discount