Got one here that is a stumper:

RCA 27F650TYX1, no pic or sometimes pic but goes out when relay
intermittently clicks and heater dims and brightens, sometimes dims
out and back on every time relay clicks. Let TV batter the relay with
time, now no picture. Relay clicking is very erratic in pattern.

Did voltages checks: 5V stable for the micro/jungle, 7V good, 22V
good and never above specs, 126V never above but when it unloads
becaue of horizontal drive cutting out voltage drops to appox 106V
then relay clicks voltage comes back up and horizontal cuts in at all
once.

Did troubleshooting tips:

Pulled crt board & vertical plug. Click click click still unaffected.
Pulled BL001 plug to disable pincushion. Still clicking.
Checked EHT (aka X-ray protect), never above 2.3V.
Checked beam sense, within specs.
Checked vertical & horizontal waveforms, all GOOD.
Scoped the cathodes for emissions, kine bia sensing come up and get
into operation when heaters is hot enough.
Checked SMPS with scope, good there too.

Flexed & smacked the chassis with no effect on that fault.

Oh YES, did cut off both plugs and solder both ends of pincushion 3
wires (two brown and one blue wires, wire order in correct positions),
have done this modifications 20 times before with success.

Sigh! Looks like either big IC (IV001?) is the blame or data bus
"dirty". Seen this before?

Cheers, Wizard