Ragebutt’s advice is good RE: maintenance. I would take the back off, make sure it’s discharged then clean around the anode cap and in general make sure there is not excessive dust/soot that could form a path for electrical discharge. Clean the anode cap with alcohol, apply a little dialectric grease to the cup and put everything back together. There is a decent chance that will help, just make sure not to wipe off the black paint on the tube - this is called “aquadag” and it is important to the operation of the monitor.