May want to do some testing of diodes and resistors while the set is
running.
Do you mean checking voltages from them? Or checking voltage drops
across them? All voltages marked on the schematics are reading
correct for chopper and line stages.

I would replace all the caps in the horizontal and drive section
because one may show good but can be bad.
I've now done that (used new ones), but to no avail. I've even checked
the non-electrolytics.

I would also replace those parts that was mentioned in one of the
previous post for parts sometimes test good but can be bad.
Also done, but still no joy I'm afraid.

But it does look like it may have a B+ problem. Is your B+ at the
proper voltage ?
Yep, spot on at 132V when set is running.

Also may want to replace your horizontal output if you have a spare
one there.
Unfortunately I don't have the necessary 2SD1880. I have a 2SD1887 but
it doesn't have the internal damper diode or base-emitter resistor.
The datasheets don't say what the resistance should be of the
internal resistor, but I'm getting 50 Ohms. I have many variations of
BU2508s and BU4808s but the ones with internal damper diodes and
resistors measure 30 Ohms B-E.

What happens when you turn the screen control on the flyback down
does it still show the line on that one side ?
Yes, it does. I am really starting to think this is a line linearity
problem. There is no adjustment in the service mode for line
linearity, so at least my lack of "remocon" may not be
important since it might not be simply an adjustment needed.

This problem can also be caused by a bad yoke. I will take a look
the schematic over the weekend and see what I may come up with. But
check your B+ line.
Did you have a look over it?

Thanks again,
James