Well you look expert on the subject and so I have an small quiz for you ..

I am knocking my head on the wall for 25 days or so, so to cure the problem on my B&O ,
related to geometry changes due the higher and lower brilliance .
Actually at very low brilliance the problem looks to move away,
but there is no static movies in this world, and so the changes is there all the time.
Check the pictures about the effect.
What I did so far , tested and replaced some caps on the primary PSU,
and so I have stable 150V ( actually 151.8V) .
About the fly-back transformer I did replaced most of the capacitors at the 1KV after the BU508.
My actual problem was that other than the waveform distortion, the horizontal was larger than what it should be,
and I had to use an smaller capacitor at the filter LC after the BU508 so to force it to shrink, originally was there one 300n/250v,
and I replaced by a 280n/250V.
It did shrink a bit , and came in to one acceptable level.
Currently I am totally confused.
The diodes that I was speaking , are also after the BU508, and somewhere I read that could be the issue.
The diodes in the fly-back transformer could also be the problem, but in this scenario, you have to replace the fly-back.
Last but not list, it could be the TDA 1940 oscillator..
I had replace all the caps around with new, but I did not see any cure.
Check and the schematic and if you have any ideas be my guest.