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from the looks of it the blanking pulses are ok, this is where a scope come in handy, knowing this ahead of time would have saved you doing all that other checking, but that's ok you are learning a valuable lesson, use that scope.
So back to the jail bars, before going there I think you need to figure out why the setup switch is not working. The reason I say that is IF there is a problem in the crt or video out transistors bias (seems to be in the setup mode anyway) THEN this could effect the cut off voltages of the CRT when it gets the bias to cut off during retrace.
Example you should be able to get rid of the jail bars if you just turn down the brightness (cut off the CRT more). Its the only thing I can think of (CRT bias).
I did notice there is a zener diode int the EC of the 3rd video out. Not sure if you checked that emitter voltage already.
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