Without looking back......
SAMS & most other SM's show wave forms & voltages with a clean signal & given pattern, it is noted in the docs. AGC can vary WIDELY from no sig / full signal.
L-R shading for me has ALMOST ALWAYS been the filter cap for the @200 V
supply. Its across all brands ! Thats hundreds of sets. Just blanking & video coupling caps were found a few times. IIRC there is one in you Sony.
As far as TNR / IF alignment go DONT DO IT ! When 17 yrs old my first TV
repair job I was told NEVER F with it or I will get fired ! He meant it. FAFO.
Yes there are a few traps you can do by eye but thats rarely needed.
time for a brew
Zeno
LFOD !