Philips Plasma cutting out when hot

Philips plasma 42PF9945 (UK spec) Chassis FTP1.1EE
I have the service manual (FWIW) and all the voltages except the 3.3v are within spec.
This tv works with perfect picture and sound, for variable periods of seconds to several minutes before cutting out and restarting, (with the interval naturally getting smaller) to finally stopping in (hard) protect.
When cooled down it will work again for a similar period.
Does the same whether in SDM or not.

The only errors I can find in the log are "FBX supply" and the 3.3v supply *is* low at a nominal 3v, which dips to 2.8V as the TV gets hot.
BUT the thing that is confusing me, is that the TV will restart on 2.8V and run for a few minutes so is this a red herring?

Replacing the PSU board is economically unfeasable, as is replacing the SSB.
I have checked the obvious candidates on the PSU, which was inconclusive. Hot air gun and freezer are getting me nowhere :(
Now wondering if it's worth replacing caps en mass and the diode for 3.3v supply (even though it seems ok) - or is this just a lost cause?

Lee
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