Disconnect the driver ( easier if it is in a socket, though if not then the driver chip is a lot easier to unsolder than the display in most cases) and measure the resistance between the 2 pins. Then check the board itself for any foreign substances between the adjacent pins, and even if there is nothing visible clean well with IPA and a good scrub, then dry with warm air and check again. this will prove if the high resistance is internal to the tube or external ( most of the time external debris is the cause, or old crusty flux residue). Then you can remove the internal leakage using a high voltage supply and a current limiting resistor, to evaporate the high resistance material, though this often runs the risk of arcing in the tube if the current is high enough or the gap is small enough.
Most of the time ghosting though is external.