Oh that's a no-brainer.
Obviously: You have a jitterbug.
(expects to be thrown bodily off the List at any moment)
You have not siad what you mean by 'jitter', and I am not a Lisa owner..
perhaps this is a symptom common to the breed. But I would ask: is it
horizontal, vertical, is the raster fragmenting, is the brightness
varying?
Is it a power supply problem that you are adjusting? If so, when it
returns, is it time related? Temperature related? I see you have made the
adjustment in Sept., but nothing since then? If it takes three months for
the problem to return, I'd be tempted to adjust for the party, then fix it
afterward....
Just my two cents, and worth every penny of it.
Cheers and Happy New Year!
John