Battery continuously empty – Questions about battery voltage

Hello, with my Kodiaq (200hp TDI, Facelift, year 2022) the battery is constantly empty. Actually, if the car is not moved for two days, it will no longer start on the third day. Come extra circumstances – e.g. the car is loaded for holidays over 2-3 hours and the door is open – it happens even without the car being moved for longer. The car was therefore already several times with the dealer – also over several days. “Found” nothing, where I am sorry he does not know what was “wanted” and how. Unfortunately I could never speak one directly from the workshop, but only the lady at the reception, who could not or did not want to tell me any details. It is a company car and I can unfortunately not drive to another workshop. Even if it is actually a tragedy, I now try to narrow down the cause myself in order to point out the workshop specifically to the cause. I therefore measured the battery voltage over a long period of time. Here the observations summarized: – completely fully charged (after a very long motorway ride) the voltage is approx. 12,65V – the battery voltage falls in total rest (car complete, everything is off, also no chargers or similar in the sockets) approx. 0.2V per 10 hours – that can be observed every night – if without only short distance is driven (several times on day 5 to 15km) the voltage tends to go down. – at approx. 12.2V the engine no longer starts. D he calculation that after a maximum of 3 days the car will no longer start, no matter how the battery was full at the beginning, is fully in line with reality… – there is never a warning before that the voltage is too low – but is always from now on no engine start possible. How would you rate the measured values? Is the quiet consumption 0.2V per night “normal” or actually a clear indication that a consumer in the car sucks the battery empty? Thanks for your help! honzaaa