When I review nonspecific reactions on an antibody panel, I always check the outdate of the reagents and the age of the specimen. Outdating reagents may show weak reactivity. Old specimens may get contaminated and bacteria may alter the RBC surfaces (e.g. T-activation).
Here is an example of weakened reactions with an outdating antibody panel. This panel was used one-week before its expiration:
Here is the same patient with the new panel with 5 weeks before its expiration: