Check the dressing/placement of the wires (yoke, focus, G2 screen, ground, high voltage). Keep the high voltage (red) wire away from chassis, sharp edges, other wires, or any source that may jab, abrade, cut, nick it.
Make sure all frame grounds are good. Be sure the ground strap/spring streched across the back of the tube is tightly touching the tube and properly connected to the neckboard and/or mainboard ground terminals.
Remember this monitor chassis needs an isolation transformer.
Make sure the anode clip under the suction cup is making a good tight connection.
If you have a high voltage probe, measure the high voltage to see if it's a bit on the high side. If it is turn the B+ voltage down a little.