Intermittent Crystal Problem
If you repair electronic equipment that uses the Crystal oscillator and if there is an intermittent problem that you can’t solve, i suggest that you replace the Crystal and retest the set again. For example, if the On Screen Display (OSD) in Monitor have problem like intermittently appear and disappear from the screen and you can’t locate the problem why not try use a hair dryer to point to the Crystal oscillator circuit area and see how’s the result.
If the problem goes away then suspect a bad Crystal and if the problem still exist then look for other area like bad CPU and etc. Do not overlook the components corresponding to the Crystal as the components can breakdown too when under load.