By the way, as to the original topic. Thanks everyone (specially @mykepredko and @Sineos for putting a lot of their time working out the issue with me). Temperature has been quite stable since I grounded the extruded body (instead of earthing it 
).
Final conclusions are that my issue was the result of a combination of factors:
- Earthing the frame due to mains heated bed
- All metal extruder + hotend
- Improper grounding of the toolhead
Fun talk. I am actually happy for going through these issues. Learned quite a bit during this mildly frustrating experience. I have quite a few projects with this printer that I still want to do slowly (like improving my (quality) speed benchy 17 minute time, which I plan to convert from cartesian to corexy). At face value It doesn’t make sense when price of a Bambu printer got as low as 700 Olafs. But then where is the fun of that?