Minor Monitor Hiccup in Ghosts'n Goblins Cab (ROMSTAR)

[Shamo]

I have a Romstar Ghosts n Goblins cab, and it works great. The picture quality, color, sharpness all look great. I have noticed though, particularly in levels 2 and above, when more sprites (or enemies) are on the screen the colors briefly invert.

Basically you will see everything in a red or white hue depending on what the original color is (white for dark colors and red for light colors). Sometimes it will briefly flicker while inverting the colors. This only lasts for a second, but occurs more frenquently in level 3 . It happens more frequently in level 3 when jerking the joystick left to right ( a technique used a lot in this game for point pressing HOWEVER this technique also generates a ton of enemies on the screen)

So im not sure if its a bad connection that is getting rocked around when I move the joystick left to right, since it happens more frequently when using this technique. Or if it is brought on when more enemies are on the screen, as the left to right technique also generates tons of enemies.

 I have never seen it happen on level 1, but I am not sure if this is becuase there arent that many enemies on the screen at one time in level one, or is it because I only use the left right technique on level 3 and its a bad connection getting rocked from the left to right. (Apon trying to recreate the problem in level 1 by rocking the joystick, nothing happened) But that doesnt explain why in level 2 it happens when 5+ enemies are on the screen at one time. Or could it be something with the board? I know this might be vague but in short:

 1) The game works fine, the monitor puts off a great picture
 2) Starting at level 2 (this has never occurred in level 1) when halfway through the level a substantial amount of enemies come on screen and the problem occurs infrequently (colors inverting once or twice a minute, but only in the part of the level where a lot of enemies spawn)
 3) In level 3 when I use a point pressing technique that goes hard left right on the joystick over and over, I can make the problem happen much more frequently (colors inverting up to 25-30 times a minute) but im not sure if this is because I am rocking the cab or again because I am generating a lot of enemies on screen.

 Any thoughts? Apologies for being so vague but these are the only 2 ways/places I can recreate the problem.

[John's Arcade]

Wow, this seems like a really odd problem. Have you checked the voltages? Make sure the 5V is cool?

[martimagico]

if you tap the cabinet hard and it happens check for connections, if it only happens when you have lots of characters on the screen id say its a processing problem on your game pcb