The adjustments on the tube base are for colour balancing, they are not geometry controls. (If you adjust those you will mess up the colour and brightness of your picture).
On modern TV's the geometry adjustments are usualy accessed using the remote handset, via a hidden service menu.
However, the cause is far more likely to be a faulty component than adjustment.
In your case, probably a leaky electrolytic capacitor in the frame output circuit.
Once set in the factory, TV geometry generally remains stable throughout its life.
Cobweb
February 2005