Recently at work two CRT monitors have developed this condition where periodically either the edges of the screen will jitter or the bottom of the screen will pull back and then snap back into place repeatedly, like the bottom of the screen is a ball being bounced on the floor. These don't seem to be the regular monitor is going out issues like vertical flipping or shrinking of the screen area in one dimension or another or going very dim, etc. I have no idea what is causing the trouble, whether it be the monitor or the on board video, but on watching the user I cannot identify any particular action which causes the screen to start bouncing, I just know that it does not happen all the time. Any help would be much appreciated. I thank you in advance for your time and your responses.