Another EU 51D550:
Default pot alignments were different.
The panel was more homogeneous.
My i1d3 seems to work with ArgyCMS, so I used it.
I tried to tweak it a lot and eventually ended up with a slightly different alignment (Yrr rotated notably clockwise, Vscan rotated very slightly conterclockwise, Vs rotated very-very slightly clockwise).
Very slight MLL improvement (~0.041 from ~0.045) but interestingly the upper end is notably lower:
60Hz full black: 0.041
96Hz black border of Dynamic Contras.mp4 with white background: 0.066
Then I carefully calibrated the TV as a D6500 (service menu hack), including a fresh ADC cal (the logic board update changed the default ADC values! They were the factory defaults from the manual this time but have been different before [134/43 or so...], so I felt I should do it and I got the usual 130/73, slightly different than in the manual).
The colors were notably better than before (I calibrated this TV before with the same equipment but right after the evil EU update got released. And I didn't check the ADC that time) and felt more neutral.
We used a lot of movie scenes to evaluate the results and it looked OK. But still there is a red push (most notable on human faces with dark scenes), just like with Pana. This seems to be a trend these days... (manual override won't help because bright scenes will be undersaturated with eye-balled color settings). But the green tinting (greenish yellows on some luminance levels) disappeared (probably the ADC). The overall PQ felt really good. I almost missed my own old D550 which I couldn't keep with the fluctuations.
"DIY certified hobby-calibrator" (based on ChadB's "warning signs" list