MacBook battery drains SIGNIFICANTLY after shut down

experts! I really hope to solve this problem as it has been drilling me for weeks now. I have a MacBook Pro 13" (2018 with Touch Bar), the A1989 model.

When I shut down my Mac, the Mac shut down correctly and I closed the lid. Left it in my desk until morning. In the morning, I felt that the Mac was warm to the touch and when I turn on, it boots up with Apple logo (like a normal startup, so it wasn’t sleeping) and it asks for my password before I could use Touch ID (so it wasn’t sleeping). BUT the battery had drained from 100% (when I shut it down) to 5%, if not completely 0 mAh left in the battery (literally 0% and won’t boot unless plugged in) when I turn it on.

I find this behaviour rather frustrating and it definitely consumes my charge cycle. When I shut it down and left it for some good 2-3 hours, it also drains around 20-30%.

Yes, I have once removed the Logic Board for cleaning (after some minor liquid damage around the iBridge Bus, which caused camera, Touch Bar, and ambient sensor to no longer work). But I made sure everything was dry and cleaned all the corrosion with 95% ethanol before putting everything back together. Couldn’t be I missed something that causes this weird problem right?

Things I have tried:

1. Resetting the SMC and NVRAM (and even T2 chip) multiple times.
2. Reinstalling macOS (I used 10.15.2 and tried downgrading + fresh install 10.14.6 to no avail).
3. Shutting the Mac down and not even touching the lid. So, left the Mac open after shut down for hours, and yet it drained too.
4. Turning off Wi-Fi before shutting the Mac down.

all to no avail.

Weirdly enough, if I just sleep the Mac, the drain was normal (just 1% drain overnight). Shut down, which was not supposed to drain any battery, was actually draining A LOT (even if need power for startup or shut down, those maybe drain around 1-5%, not 20%).

Please advise me on what to do. Thank you so much :))