After imprints, Actives are wiped back to their "tabula rasa" state, and are not supposed to retain memories of their former lives or their previous imprints. However, this process is not perfect, and an active may remember certain events or behaviors. Psychoactive drugs, head injuries or emotional stress may contribute to glitching.
The Dollhouse staff views this as a problem, as it makes Actives difficult to control and interferes with completing their engagements. Glitching may also be a precursor of a composite event.