A "dry joint" is one where the solder has lifted from one or more of the points it was meant to connect. These will often cause intermittent symptoms, or ones that come on or go away when the system has had time to warm up.

Thermal expansion and flexing can make or break the "dry" contact. Service folk (at least those who still do component level work) will narrow down the location of the dry joint with a can of coolant spray - hit the bad joint, it cools, contracts and breaks contact. Then visual ID with a magnifier.

A two second touch up with a decent iron, perhaps a smidgelet of more solder and/or flux, and Bob is your mother's sister's husband again.