What's the harm in sending this part to Matt to analyse properly if there is no chance of a warranty replacement anyway? Whether the spacer was there or not, the failure could still be down to a manufacturing fault, which coincidentally happened to line up with some other features of the assembly. A lecturer at uni had a car part fail which the manufacturer told him was not covered under warranty because it was caused by bad driving style. He took some images using an SEM which clearly showed a casting defect resulting in a weak point in the part, sent them to the manufacturer, and they paid for the replacement