I documented in another thread where my folks' Model 3 suddenly started draining 3-5 kwh per day for several weeks while parked, for those counting, that's a constant 125W power draw or constant 10-15A current draw:
Tesla says "Gray area for the warranty" and says I drained it [12V covered under warranty - resolved]
There are no 3rd-party accessories in the car, no use even of the in-car apps (no Sentry or anything), and it was hardly driven during those periods. I have a detailed timeline documented there with lots of timepoints from a remote logger - the only things that might've been coincident were a firmware update, and a 12V battery warning (one time). It started suddenly a few days after the firmware update when the vehicle was parked, and stopped suddenly weeks later without any new firmware update also while parked. In between, since the 12v battery was being cycled repeatedly the whole time, it was replaced a few days AFTER the drain stopped.
Given the absence of other activity other than a few short trips over those weeks, I could only guess one of two possible causes:
-a bad firmware update - not necessarily that the firmware itself was bad, but that an update without a hard reboot could've caused some app to misbehave and run constantly, and prevent the car from sleeping. This could've caused an eventual end to the 12V battery, though it was already 3.5 years old.
-a bad 12V battery - it was already old, a warning did pop up once before the start of the high drain, and a failing 12V battery could cause many of the electrical systems to misbehave, thus causing some of the software apps to misbehave, thus further causing the car to not sleep, etc.
I'm tending to believe it was the latter, that a bad 12V battery can cause all sorts of subsequent misbehavior, including high drain and deep cycling of itself. Which is to suggest that in the OP's scenario, it could've been the Hansshow or it could have been an end-of-life battery to begin with. Probably the Hansshow wasn't necessarily drawing the 3A itself, but over time its own power usage could've accelerated the cycling and decline of the 12V, causing the car itself to misbehave. Or just the old age of the 12V being the root cause.
Who really knows, but knock on wood, our own two Tesla's 12V original batteries are 4 and 5 years old respectively, I should get them both replaced soon...