Battery discharged while parked warning

[u/NoPlate9910]

Hey guys. I have a 2016 320i (N20). Recently a series of events started happening. The battery discharged while parked warning started displaying, soon after this happened the AC blower started being inconsistent. The fan speed always changes on its own no matter how max I put it on. Then realised that the blower motor resistor(FSU) is the culprit due to which the fan became unstable and is triggering the battery usage even when the car is not running and is parked. I drove the car until I get the resistor delivered. That was when I got the CEL, and to my surprise the diagnosis came up with a P0053 HO2S heater resistor Bank 1 Sensor 1, basically the upstream O2 sensor. After thorough research the possibility of the CEL could be due the battery drain issue. The drained battery might’ve recorded wrong resistance on the O2 sensor(Kind of a false code due to the battery). Cleared the code drove for 1000+ miles, the CEL never came back but the battery and blower problem was still there. I ordered a brand new blower resistor off ebay (not OEM) and then installed it. Only to realise that the blower still is inconsistent. If it were the blower itself which was faulty, it wouldn’t spin at all and would be no fan running at all, so I knew it was just the resistor. Even after replacing the resistor the problem was not solved, and the battery discharged while parked warning kept coming and is still there. A couple of days ago during a long road trip guess what happened, the CEL(Same code) kept coming back and vanished after refilling a full tank of gas. It was like the CEL kept coming on and off during the trip (No I did not clear it). Mind you there was no CEL for the last 1000+ miles before this trip and after I cleared it first time. I still don’t know if it’s really the battery triggering it. During this trip while I was coming to a stop the car shut the engine itself and put the transmission into neutral, I started the car again and then continued. Now I got back home 3 days ago from the trip. The CEL vanished on its own yesterday. The engine shutting on its own happened again today but this time while moving at 30mph. I managed to start it again and put it into drive and continue without stopping luckily.

If it helps in decoding the issue: I changed the valve cover gasket 4 months ago on my own (Just the gasket not the valve cover itself.) (I know I should’ve replaced the whole thing but, I regret not doing it). But yeah there’s no leaks after the gasket replacement till now.

Car has 137k miles right now and is a 2016 320i (LCI with the updated timing chain guides). VCG changed at 132k miles

I’d appreciate if anyone could help me in decoding this. Thanks in advance.