I wanted to document this here for anyone with the same issue and for my future self (hey dude, you look awesome

)
Anyways, this came to me as a previously capped K7000 19". There was also a new flyback installed. The screen would do a slow motion hula but was otherwise bright and clear.
I pulled the str3123 (which is electrically the same as a str30123 with pins 1 and 3 reversed) and checked it against a known good one (virtually the same values as posted for the str30130 located in the FAQ here on this board). Anyways, it came up as different so I swapped in the good one...no change.
There was already a new filter cap installed and the voltages came up ok so I pulled the C36 safety cap and replaced it with another one.
That did it--rock solid picture after that.
Hope that helps someone...