Coincidence due to age? Maybe. What I find mostly is the cap will be
marginal. After the set is plugged in a while it all warms up and the
B+ seems to be close enough to the ideal 143V. But when the set is
cold, the B+ is higher. Typical bad capacitor problem.

A 10% increase in B+ on start up is a 10% increase in HV, 28,000 volts
is quite a lot less than 30,800 volts.

They do have the unit regulating at start up. The standby rough
regulator feedback is doing the regulating, when it fails to regulate
on the money, there is nothing that will keep the set from coming on,
until it goes so high that there is a catastophic failure.

So as always, check/replace the capacitors in the smps and cr4118
everytime.