Thank you for your analysis.
I did check firmware update in Installer mode and it says no update available. My software version is 20.51.2 while all others have 21.xx.x .
I did hear liquid noise in my inverter occasionally. However, I don't think the inverter is over-heating. It is outdoor on a shading wall without sun light. Fan was not running anytime (defective? I also heard the inverter was singing consistently when power output was high.
I agree that even w1 got clipping, since power output is consistently slightly higher in parallel mode.
I hope to get peak power close to ~6.5kw if clipping issue is resolved. Not sure if Tesla can/will help.