On a bar top with a drop in monitor there is a plastic cover over the monitor.
Pull the monitor out of the machine, remove the plastic cover, and with a compressor blow all of the dust off of the back of the tube.
You could have some stray high voltage creep due to excessive contamination.
It could also be you high voltage lead to the back of the tube is not clamped in properly.
You could get a long flat-blade screwdriver and hold it's metal against the metal frame of the monitor as you slip the blade under the high voltage cap to discharge any high voltage stored inside the tube then peel back the rubber cap to see if the wire clip is set deep into the glass hole of the tube.
It could also be your monitor is failing and needs to be repaired, at the very least it could need a cap job.