Illya,
once again, you designed a really nice board!
You mentioned in the video, that you designed in a low pass between the LTZ reference and the AD OpAmp, to suppress the chopper spikes going backwards into the reference circuit.
Well, I doubt a bit that this effect is so important.
You also introduced a lot of solder junctions between the LTZ and the OpAmp, that may ruin your T.C., or you have to balance all these junctions, as it's been done in the 3458A DCI circuit, you remember?
Anyhow, in my in own Spartan single-sided design, I directly (copper-wise) connected the LTZ output to the LT1052 ChopAmp, accepting possible spike feedbacks, but avoiding thermo junctions..
We'll see in 1 year time, what will happen,... and I just started a noise / stability measurement on the 10.000V output, realized with these ordinary BMF from AE.. we'll see tomorrow.
Frank