These cars use a CAN bus system and a module might be staying awake / waking up at random even when there isn't any traffic on the CAN bus.

As an example of how CAN works, this is where a module resides in a door and is fed with power / ground / 2 wire CAN communication. This module controls / power window / mirror / seat controls / door light / dome light / door lock. Messages are sent from a switch or other system over the CAN and when a module hears a specific command, it performs a function.

I'm being told that some modules can stay awake for 2 min so you might have to wait longer.

I have seen alternators have a shorted diode ( actual short not the term some apply to every electrical failure ) and cause a drain. Amp clamp the battery wire at the alternator and see if there is a drain. Also with key off, place a screw driver against the back of the alternator / pulley shaft and see if it is magnetic, is so the alternator is failing.

I have seen electrical drains come and go due to water intrusion or a failed capacitor that leaked. I'm pretty sure your type of car has a problem with water getting into the passenger side of the dash so do some research on that.