I had this problem on my 2016 model from delivery - I bought it at 3 yrs old (the car, not me!) Had several trips back to the main Skoda dealer who carried out the mandatory battery load test and carried out a full diagnosis before proclaiming everything OK. Then I had a very interesting conversation with the service receptionist who knew about things other than word processers. Her partner was a tech for a BMW dealer and they have the same problem. But it's limited to PETROL engines. Her car was a petrol BMW Mini and she had had the same problem several times. She said that partner had told her that it was a known problem across makes in the industry but NOT with diesel engines. And it also seems that no one quite knows the reason why (petrolgate?).
I can cofirm the lack of problems with diesels as I drove various makes over long distances as a field service engineer. Never once did a diesel fail to carry out its stop/start regardless of season, load etc. From discussions with technicians all loads like lights, aircon, wipers, entertainment and so on are part of a complex programme that give different results on different days. Who remembers when an 'on' button turned something on? Finally, I have noticed than when the dealer has performed a service and reset the sevice indicator or checked codes the S/S works perfectly for a couple of days.
Not sure if this answers any of your questions, but it should provide some fuel for thought. Just remember, the ignition key works fine.