This is going to be a pain to sort out.
The usual culprits are dodgy door handles
Faulty alarm module
Some part of the mmi keeping the systems awake which i would be inclined to try first as you said the handles all work as they are meant too.
If you buy from eBay a most fibre bypass loop you can isolate parts of the most loop with it and unplug that module to narrow down which device is doing it.
Or if you are handy with a multi meter you can measure the voltage drop over fuses to find the culprit.
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