Got a very similar problem with our dreaded Mazda CX60 PHEV. On paper lovely car, in reality absolute lemon without the benefits that an actual lemon would bestow!!
Don’t use it much but deliberately took it to Burnley and drove in petrol mode to ensure alternator was charging the battery for the following day. Or so I thought!
Plugged in overnight and drove to my daughters physio session in Morley. 2 and a half hours later, not a thing working. RAC man tested 12v battery and it indicated 4.7v!!!
Cannot for the life of me work out what could drain the battery so quickly?
Eventually got home and RAC coming Monday to put another battery in at the cost of £311 to Motability. Which will probably end up lasting weeks, by which time I can only hope the thing has gone back. I’m seriously considering just doing without it’s just such a pathetic excuse of a vehicle. Worst car ever. Best car ever – £150 20 year old VW Polo Bread Van. Difference in price ~£55K!!!!