Just adding my experience to the pile. I leased a CX-90 PHEV at the beginning of June. About a month later, at ~1500 miles, it had a hybrid system malfunction. I tried to start it and it threw a whole series of errors, ranging from "Push button start malfunction", "Charging system malfunction", all the dash lights were flickering and flashing, the brake pedal was "pumping back" at me, like the ABS system was activating for no reason. After a few minutes of that, everything just died. No lights, no buttons, no door locks, etc. Completely bricked.
Luckily this all happened in my driveway. Like everyone else here, or so it seems, we bought this car because we have kids and a newborn baby to haul around town and needed the 3rd row.
Also like others have experienced, we had issues with the Mazda towing service not sending out the right tow vehicle the first time and not being able to put the transmission in neutral when everything is dead.
The dealership ran their diagnostics and claimed the issue was caused by a faulty 12v battery, which they replaced. That was about 700 miles ago and it has been running fine since then, but just yesterday I had a "Low battery mode - Run engine to charge 12v battery" message (or something along those lines, I didn't get a photo in time). That warning combined with the previous issue has me pretty paranoid today.
I spoke with the dealership and they are trying to tell me that this is a normal warning to see occasionally in this vehicle, but their explaination has not been consistent. They originally told me that there is no alternator and that the 12v battery is charged off the high-voltage system, but now that I am getting the low battery warning, they are telling me that I need to be running the gas motor more often to make sure the 12v stays charged.
At this point I don't believe anything coming out of Mazda or the dealership about this issue and am just waiting for it to happen again. I personally think the issue IS related to the 12v battery, and a bunch of the modules in this vehicle do weird things when the 12v battery it totally flat. I just think there is a different underlying cause that is either draining the 12v batteries or just not recharging it adequately.