Ceronix 1492 - Only gets blue when ya smack it

[mwade109]

My PE+ slant top video poker will only get blue when you rattle the monitor, knock on the glass or otherwise 'smack it' and then it simply goes away as quickly as it appeared.  Because it is in a slant top and the monitor is upside down there isn't any logical way to tap on parts while it's running to try to narrow down the loose connection is.... if indeed it is a loose connection.  Any ideas about this? Am I looking at the wrong avenue thinking its a loose connection?  It works great with the black background..... it kinda just annoys me.  Thanks!
-mike