Condensation is not one phenomenon. Where it forms tells you what is happening, and the three cases have entirely different implications.
Interior surface condensation — moisture on the room-side face of the glass — indicates that indoor humidity is meeting a surface below the dew point. It is usually a ventilation and humidity issue rather than a window defect, though it is more pronounced on poorly insulated glazing.
Exterior surface condensation is counterintuitively a sign of good performance. It means the outer lite is staying cold because so little heat is escaping through the unit to warm it. High-performing glazing does this on clear autumn mornings.
Condensation between the panes is the only case that indicates failure. The perimeter seal has been breached, the desiccant is saturated, and moisture is cycling inside a cavity that cannot be cleaned. No drilling, venting, or defogging treatment restores the insulating cavity or the seal.