Doing some work on the non-gate array model 4 earlier today.
Sometimes the video would shrink & grow after the machine's heated up, like there's a loose connection, or maybe a bad solder joint.
Solder joints seem solid. Seems to have been the connector on the ribbon connecting the video board to the PS and main board. The card edge connector that the ribbon connects to (at the video board end) was really dirty and fairly loose.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko